Answer:
$20.00
Step-by-step explanation:
Let x be the money Carrie had at the start of the week.
Add/Subtract from this amount (x) for the events occurring during the week:
x Start
-3.50 1 book
+1.25 Sugardaddy income
-7.50 Batman movie
===============
The end of the week Carrie has $10.25
Put this into one equation:
x - 3.50 + 1.25 - 7.50 = 10.25
x = 10.25 + 3.50 - 1.25 + 7.50
x = $20.00