Melanie's weekly allowance is $18
Step-by-step explanation:
let Melanie allowance = b
She spent half of it on movies = 1/2 × b = b/2
Amount left after removing movie cost = b - b/2
Then earned an additional $9 = (b - b/2) + 9
The total money Melanie has now = $18
b - b/2 + 9 = 18
Hence, Melanie's weekly allowance is $18