Answer:
36 minutes
Step-by-step explanation:
It takes 45 mins to deliver paper on her route.
Let X be the amount of time it takes the brother to complete the route.
The brother works at the rate of 1/x route per min
The girl works at the at the rate of 1/45 route per min
Girl and brother working together works at rate of 1/20 route per min
1/x + 1/45 = 1/20
Multiply through by 180x
180 + 4x = 9x
4x - 9x = -180
-5x = -180
x = -180 / -5
x = 36 mins.
It takes the brother 36 minutes to complete route alone.
