\[ 12x + 9y - 2x - 5y = (12x - 2x) + (9y - 5y) = 10x + 4y \]
\[ (4a + 3) - 3(2a - 1) = 4a + 3 - 6a + 3 = (4a - 6a) + (3 + 3) = -2a + 6 \]
Ответ: а) 10x + 4y; б) -2a + 6.