I think the answer is he payed $3.40
Square Perimeter = 4(4x-1)
Rectangle Perimeter = 2(2x+1) + 2(x+2)
Square Perimeter = Rectangle Perimeter
4(4x-1) = 2(2x+1) + 2(x+2)
16x - 4 = 4x + 2 + 2x + 4
16x - 4 = 6x + 6
-6x +4 -6x +4
10x = 10
x = 1
To solve this problem we will start by calculating time needed for each of them to fill the pool.
We have formula:
Volume = rate * time
Or
time = volume / rate
Wilma:
time = 9900 / 900
time = 11h
Betty:
time = 9900 / 500
time = 19.8h
Now we substract these two numbers:
time_difference = 19.8 - 11 = 8.8h
Betty needs 8.8 hours more than Wilma to fill the pool.
0.4 and 0.4 or 0.8 and 0.2
Hope this helps :)