Question

if 145 students surveyed and 76 choose cheese and 16 choose vegetable and 53 choose pepperoni if there is 580 students in the school how many pepperoni pizzas should they order

Answer 1

Proportion wanting pepperoni = 53/145.
Estimate for 580 students = (53/145) × 580 = 212.

So about 212 students would want pepperoni.
If you mean whole pizzas (not one pizza per student), divide by how many people one pizza serves and round up. For example, at 8 slices (about 8 people/pizza) you'd need 212/8 = 26.5 → 27 pizzas.