SAT PREP question.

Question

A restaurant has 15 tables that can seat a total of 78 people.some of the tables seat six people, while the remainder of the tables seat four people.How many tables seat six people.

Answer 1

Let x = # of tables seating 6 people

Let y = # of tables seating 4 people

 

x + Y = 15 tables

6x + 4y = 78 people

Solving for (1), x = 15 -y)

Substituting in (2),  6(15-y) + 4y = 78

Solving for y, y = 6

Thus x = 9

9 tables seat 6 people.