How to solve this because i'm really comfused

Ashopper bought a watermelon a pack of napkins and some paper plates in his state there was no tax on food the tax rate on non-food items is 5% the total for the three items he bought was 825 before tags and he paid $0.19 in taxes how much did the watermelon cost

Which is an equation for the nth terms of the sequence 12,15,18,21

You call the pizza store and find out that eachpizza has 12 slices. you expect 16 people tocome, and you estimate each person will eat 3slices. how many pizzas should you order