Answer :
Well, let's undo the earn. He had $10. He spent half of the original, so [tex]x-\frac{x}2=10[/tex], or [tex]2x-x=2*10[/tex], or x=20. So, the weekly allowance is $20.
His weekly allowance is $20.
Explanation: Since he ended the week with $17 and we know he earned $7 from washing a car, he had $10 before he earned the extra $7. We know he spent half of his allowance at the movies, so $10 is half of the amount that he had before he went to the movies. $10 is half of $20, so his allowance is $20.
I hope I could help! :D
