The difference between your and you're

Good communication skills. Being able to tell someone else what you mean so they or anyone else could understand. My boss is beyond awful at it makes getting anything done a struggle at times.

Basics of money.

Like putting away one third of your money every month, keeping a budget, learning when to splurge to maintain self control (budgets not too tight) and learning to live below your means at any cost.

The magic part is the other half of that equation. Money grows in it's own (though slowly) and putting some away for later starts paying for its own pretty soon.

Basic humanity/empathy for marginalised groups

Critical thinking skills.

It just astounds me when people who should know what this is and how to practice it, don't.

The difference between your and you're.

Knowing the absolute basics of using a computer

Looking up the information online (beyond just googling it in your native language).

i.e. Trying out the results in other search engines, when looking for the information about something in a foreign land, or something the specific nation is very good at; try using the local language (and use the online translators to search it and read it).

Apparently a lot of older people were never taught algebra. I have a lot of math in my life so I find that weird.

A basic skill that I lack is the habit of keeping things clean. I do my cleaning in bursts, which can be counterproductive because my space is messy between those bursts. It's a basic skill, and one that I'm working to improve, but it sure does not come naturally to me!

Knowing how to swim or ride a bike. It's not too common, but when someone tells me they can't, I'm quietly kinda shocked.

The difference between "your" and "you're."

critical thinking

Empathy. It shocks me how many "adults" have a toddler-level understanding of their relationship to the world (as in it doesn't revolve around them) and society (as in we have responsibility for each other). So many "adults" sound like screeching toddlers whenever there's a hint of someone else getting something they don't get. It even reaches the level of "I don't like this movie so it shouldn't have been made" as if the very existence of entertainment or education or whatever in a field they themselves don't prefer is a personal affront.

And this isn't even a right-wing thing. The feminist National Action Committee in Canada was turned from a potent and feared political force to a laughingstock by ostensible left-wing women deciding that their concerns over daycare trumped native women's active murders among other intersectional issues.

How to reason through solving a problem or fixing something. Not necessarily being successful, but just the process of thinking about possible things to try or steps to take.

Taking feedback constructively

Cooking & self reflection

Listening to understand, rather than listening to respond.

Imagining the potential of a prototype.

"So with this prototype I want to explore aspect A"

"I don't like it. I don't want this as a final product."

"Ok. Do you like aspect A? Imagine all other things were finished as you like it."

"No, I don't like this product."

Math, and I mean basic math: adding, subtracting, multiplication, division. Basic understanding of fractions, basic understanding of percentages.

I'm not amazing at math but I consider this basic and with relatively regular day to day application. I'm not saying people should be able to make these operations without a calculator on the fly, I certainly couldn't in many cases. But I would expect people to know what math you need to apply to, say, calculate a 20% discount. I would expect people to know if, say, two thirds is more or less than three quarters. But no. Nope

How to cook? Or even follow a recipe. Not like hard stuff either, a simple casserole recipe or cookie recipe. Not even find a good recipe, that's actually very hard online these days what with bullshit generators and stuff. I hand you a recipe.

To do very basic home repair and DIY. I keep wondering how people get through life without being able to drill a hole, fix a clogged drain or even change a light bulp. Do they get some sort of service technican for all these things?

Same as most kids don't know. there are a number of things. Money, listening, how/who to gather information from. I'm missing your point when you put adults in your question.