What does it mean for an equation to express y in terms of x?

What is the value of f(x) = 2.2 for f(-2)?

When george started his current job, his employer told him that at the end of the first year, he would receive two vacation days. after each year worked, his number of vacation days will double up to five work weeks (25days) of payed vacation. how many vacation days will he have in 4 years

During how many months was the difference between the number of days with homework and with no homework greater than 6?