Answer:
Step-by-step explanation:
As they are in proportion,
x +4 : x +12 :: x -1 : x + 5
Product of means = Product of extremes
(x + 12)(x -1) = (x +4)(x+5)
Use FOIL method for polynomial multiplication
x*x + x*(-1) + 12*x + 12*(-1) = x*x + x*5 + 4*x + 4*5
x² - x + 12x - 12 = x² + 5x + 4x + 20
Combine like terms
x² + 11x - 12 = x² + 9x + 20
x² + 11x - 12 - x² - 9x - 20 = 0
Combine like terms
x² - x² + 11x -9x -12 -20 = 0
2x - 32 = 0
2x = 32
x = 32/2
x = 16
