1)х+20=68, х=68-20,х=48, проверка: 48+20=68,68=68. 2)68-12=20+y, 56=20+y, y=56-20, y=36, проверка: 68-12=20+36,56=56. 3)m-12=68+12,m-12=80, m=80+12, m=92, проверка: 92-12=68+12, 80=80.
12 : (4/5х) = 20 : 1/4 5/6 = 15/(2х - 3)
4/5х * 20 = 12 * 1/4 5 : 6 = 15 : (2х - 3)
80/5х = 12 : 4 6 * 15 = 5 * (2х - 3)
16х = 3 90 = 10х - 15
х = 3 : 16 90 + 15 = 10х
х = 3/16 105 = 10х
х = 105 : 10
х = 10,5
(15/2)/(9/2) = х - 3/25
15/2 * 2/9 = х - 3/25
15/9 = х - 3/25
5/3 + 3/25 = х
х = 125/75 + 9/75 = 134/75 = 1 59/75
12х+20=68 х-20=68 12+х=20 68-х=12+20
12х=68-20 х=68+20 х=20-12 68-х=32
12х=48 х=88 х=8 х=68-32
х=48:12 х=36
х=4