You can put this solution on YOUR website! If y varies directly with x
y = kx
---------------
Now solve for "k":
and y = -4.5 when x = 13.5,
-4.5 = k*13.5
k = -1/3
--------------------------
find x when y = 24.
24 = (1/3)x
x = 72
======================
Cheers,
Stan H.