a) 3x(12x – 4) – 9x(4x – 3) = 30
3x .12x – 3x . 4 – (9x . 4x – 9x . 3) = 30
36x2 – 12x – 36x2 + 27x = 30
(36x2 – 36x2) + (27x – 12x) = 30
15x = 30
x = 2
b) x(5 – 2x) + 2x(x – 1) = 15
(x . 5 – x . 2x) + (2x . x – 2x .1) = 15
5x – 2x2 + 2x2 – 2x = 15
(2x2 – 2x2) + (5x – 2x) = 15
3x = 15
x = 5.