А (12 + 3у) : 21 = 6
12 + 3y = 6 * 21
12 + 3y = 126
3y = 126 - 12
3y = 114
y = 38
Б) 45 - 2(3x - 8) = 31
2(3x - 8) = 45 - 31
6x - 16 = 14
6x = 14 + 16
6x = 30
x = 5
в) 6y - y - 35 = 50
5y = 50 + 35
5y = 85
y = 17
А (12 + 3у) : 21 = 6
12 + 3y = 6 * 21
12 + 3y = 126
3y = 126 - 12
3y = 114
y = 38
Б) 45 - 2(3x - 8) = 31
2(3x - 8) = 45 - 31
6x - 16 = 14
6x = 14 + 16
6x = 30
x = 5
в) 6y - y - 35 = 50
5y = 50 + 35
5y = 85
y = 17