Basic arithmetic, elementary and HS education and - true story;
Last Monday I went to McDs drive thru - ordered a bacon/egg biscuit and a large diet coke. Voice says that'll be Five dollars and 2 cents please drive forward.
Hispanic kid in window is about 15 maybe 16 - I hand him 2 pennies and a 20 dollar bill.
He looks at the money I gave him with a confused look on his face. Still looking confused and moving his lips like he's talking to himself he opens his cash drawer and starts digging in the coins and pulling one dollar bills
I stop him by saying "just give me a 10 and a 5 we'll be good. He says I don't have any tens...I said ok give me three 5s...he looks even more confused.
I said the charge is 5 dollars and 2 cents right? He says "yeah" - I say "I gave you a twenty and 2 pennies my change is fifteen dollars"
He keeps staring at his cash register trying to figure out how to calculate the change for the $5.02 charge. He gives up - shakes his head and looking like he's going to get in trouble he drops the coins and the one dollar bills back in his cash drawer and pulls 3 fives and hands them to me...I can tell he thinks it's not right and that I cheated him somehow.

At the next window where I pick up my food there are people there who only speak Spanish so I don't bother telling anyone that the kid in their collection window can't add and subtract.

The Hispanic kid taking the money was very Americanized - I suspect he was born and raised here in my town -spoke perfect English without any accent. But like most kids in public education he had no functional understanding of basic arithmetic. I don't blame him for that - I blame his parents and the system of public education.