(2x) / (x + 4) = 3 / (x - 1)
2x * (x - 1) = 3 * (x + 4), " cross multiplying"
2x^2 - 2x = 3x + 12, " removing braces"
2x^2 -2x - 3x - 12 = 0, " bringing all terms to L H S"
2x^2 - 5x - 12 = 0, " simplifying"
2x^2 - 8x + 3x - 12 = 0
2x (x - 4) + 3* (x - 4) = 0
(x - 4) * (2x + 3) = 0
color(blue)(x = 4, -3/2