(17 • 2x) - (11 • x) = 46
(34x) - (11x) = 46
23x = 46
23x/23 = 46/23
x = 2
Area is equal to L•W. So 17•2x is total area. But you only know that the shaded area is 46. So you have to subtract the non shaded area from the total area and use the work above to get x.
