20x + 17 + 4(2x - 3) = 3(7x + 4)
20x + 17 + 4 * 2x + 4 * (-3) = 3 * 7x + 3 * 4
20x + 17 + 8x - 12 = 21x + 12
20x + 8x - 21x = 12 + 12 - 17
7x = 7
x = 7 : 7
х = 1
проверим:
20 * 1 + 17 + 4(2 * 1 - 3) = 3(7 * 1 + 4)
20 + 17 + 4*( - 1) = 3 * 11
37 - 4 = 33
33 = 33