Alfred's rate is 1 house per x days or 1/x house per day.
Bill's rate is 1 house per y days or 1/y house per day.
If Alfred can only do 2/3 as much work as Bill
So 1/x = (2/3)(1/y)
or 1/x = 2/(3y)
Alfred and Bill working together can paint a house in 24 days.
Their combined rate is 1/x + 1/y house per day.
their combined rate times 24 days = 1 house painted. So
(24)(1/x+1/y) = 1 house painted
So we have the system of equations:
Simplifying
Substitute 2/(3y) for 1/x in the second equation:
Divide both sides by 3
Substitute in
Multiply through by LCD = 120
Edwin