Question 760439
Base = x
Height = (x - 5)
Area = 1/2 (base * height)
  42 = 1/2 (x*(x - 5))
  42 = 1/2(x^2 - 5x)
  84 = x^2 - 5x
  x^2 - 5x - 84
(x - 12)(x + 7) = 0
x = 12
x = -7 (no answer)
Base = 12cm
Height = 7cm