1)
a)(-0.5y) * 20 *(-3x) = 30xy
b)(-a + 3b -1.2)*5 = -5a + 15b - 6
в)-2.1(x-2y+3)= -2.1x + 4.2y -6.3
2)
a)4.6a - 4b - (-3.8b + 3.5a) = 1.1a -0.2b
b)2a - (8 - a) + (3a - 2) = 6a-10
в)8 - 6(2x - 1/2) + 12x -2 = 9
3)
3(0.9a - 1.5) - 1/2(3a - 9) = 2.7a - 4.5 - 1.5a + 4.5 = 1.2a = 1.2 * (-1/3) = 6/5 * (-1/3) = -2/5