Question

the number of pizzas eaten at the class party is equal to one-fourth and number of students plus two more pizzas for the adults if 9 pizzas are eaten how many students are there

Answer 1

If s represents the number of students, then the number of pizzas is
  s/4 + 2 = 9
  s/4 = 7 . . . . . . subtract 2
  s = 28 . . . . . . multiply by 4

There are 28 students.