Answer:
She will pay $1092.50 because .15x950 is 142.50 and if you add that to 950. you get $1092.50

Look at the square root like "x", then
First take 400 and divide it by 2.5 to find the hourly rate. Then divide 600 by the hourly rate (160) to get 3.75 hours. My work is listed below.
If i'm not wrong its distributing property of addition. <span />