a) 660 = 33x => x = 20.
б) 4z = 92 + 350 => 4z = 442 => z = 110.5.
в) 83 + 49 = 3x + 8x => 132 = 11x => x = 12.
г) 43 - 27 = -9z + 7z => 16 = -2z => z = -8.
д) 41 = 34y - 23y => 41 = 11y => y = 41/11.
e) 21x = 122 + 34 => 21x = 156 => x = 156/21 = 52/7.