Posted by loulou on .
frank can wash the car in 2/3 the time his younger brother,joe,can wash the car.they worked together and washed the car in 40 minutes.how long would it have taken each boy working separately?

algebra 
Henry,
X min. = Joe's time.
2x/3 = Frank's time.
1/x + 3/2x = 1/40
Multiply both sides by 2x:
2 + 3 = x/20
x/20 = 5
X = 100 min. = Joe's time.
2x/3=200/3 = 66.67 min. = Frank's time.