Answer:
Her weekly allowance is $10
Step-by-step explanation:
Let's call x her weekly allowance
At the end she has $12. She obtained this for the addition of the money she earned cleaning windows ($7) and the half of her weekly allowance (the other half she spend it at the movies). Mathematically:
x/2 + 7 = 12
Solving for x:
x/2 = 12 - 7
x = 2*5
x = $10