Jason spent half of his allowance going to the movies. He washed the family car and earned 7 dollars. What is his weekly allowance if he ended with 15 dollars?

Let x equal his allowance.

He earns $7 for washing the family car.

His total intake is x + 7

He spent half of his allowance going to the movies.

This means he spent 1/2 * x going to the movies.

He has $15 left.

You get:

x + 7 - 1/2 * x = 15.

Combine like terms to get 1/2 * x + 7 = 15.

Subtract 7 from both sides of the equation to get 1/2 * x = 15 - 7

Simply to get 1/2 * x = 8

Multiply both sides of this equation by 2 to get x = 8 * 2.

Simplify to get x = 16

His allowance must have been $16

He washes the family car and earns $7.

He now has $23.

He spends half of his allowance, which is $11.50 on the movies which means he spent $5.75 on the movies.

He now has $23 - $5.75 = $17.25.

His allowance had to be $16.