For what value of x will (3 + x)/(5 + x) and (1 + x)/(4 + x) be equal?
3 + x 1 + x
____ = ______ cross-multiply
5 + x 4 + x
(3 + x) ( 4 + x) = (5 + x) ( 1 + x) simplify
x^2 + 7x + 12 = x^2 + 6x + 5 subtract x^2 from both sides
7x + 12 = 6x + 5
7x - 6x = 5 - 12
1x = -7
x = -7
