Write an equation

Question

Write an equation for an auto dealer has 468 cars. He has three times as many four-door cars as two-door cars. How many two-door cars does he have?

Answer 1

Let's say that x = number of 4-door cars and y = number of 2-door cars. The first sentence can be written as

 

x + y = 468

 

The second sentence can be written as

 

3y = x

 

These two equations are enough to solve the whole problem:

 

(3y) + y = 468 --> y = 117

x = 3 * 117 = 351