Answer: his weekly allowance is $8
Explanation:
Let x represent Tim's weekly allowance.
Tim spent half his allowance on the movies. This means that the total amount that he spent on the movies is x/2. The amount remaining would be x - x/2 = x/2
He washed the family car and earned 8 dollars. This means that the total amount left with him is
x/2 + 8
if he ended up with 12 dollars, it means that
x/2 + 8 = 12
x/2 = 12 - 8 = 4
x = 2 × 4 = $8