Ineed on 21 a-c, i don't understand how to do it

Idon’t understand this.. will someone ? will mark brainliest along with 20 points.

Me! last question, and i'm stuck! write the algebraic expression that models the word phrase. the product of 2 divided by the number h and 8 more than the number k

If mary had 320 toy cars and she gave her friend 50 cars and then she gave her brother 72 more cars how much toy cars would mary have left ● explain with proper details