Пошаговое объяснение:
1.
8у + 3 = 10у – 7
10y - 8y = 3 + 7
2y = 10
y = 10:2
y = 5
2.
6 – у = 3(3у – 8)
6 - y = 9y - 24
9y + y = 6 + 24
10y = 30
y = 3
3.
5(х +12) = 7х + 4
5x + 60 = 7x + 4
7x - 5x = 60 - 4
2x = 56
x = 28
4.
– 2х + 16 = 5х + 30
5x + 2x = 16 - 30
7x = -14
x = -2
5.
– 12а – 3 = 11а – 3
11a + 12a = -3 + 3
23a = 0
a = 0
6.
6 – 2х = 8 – 3х
-2x + 3x = 8 - 6
x = 2
7.
3в + 5 = 8в – 15
8b - 3b = 5 + 15
5b = 20
b = 4
8.
11 – 5у = 12 – 6у
-5y + 6y = 12 - 11
y = 1
9.
2 – 5а = а +14
a + 5a = 2 - 14
6a = -12
a = -2
10.
15х – 3 = 10х + 12
15x - 10x = 12 + 3
5x = 15
x = 3
11.
6 – 2у = 8 – 3у
-2y + 3y = 8 - 6
y = 2
12.
3а + 5 = 8а – 15
8a - 3a = 5 + 15
5a = 20
a = 4
13.
11 – 5х = 12 – 6х
-5x + 6x = 12 - 11
x = 1
14.
4(3 – х) – 11 = 7(2х – 5)
12 - 4x - 11 = 14x - 35
1 - 4x = 14x - 35
14x + 4x = 1 + 35
18x = 36
x = 2
15.
6х + 10 = 4х +12
6x - 4x = 12 - 10
2x = 2
x = 1
16.
7х + 25 =10х + 16
10x - 7x = 25 - 16
3x = 9
x = 3
17.
3у + 16 = 8у – 9
8y - 3y = 16 + 9
5y = 25
y = 5
18.
4(6у – 7) = 5(3у +7)
24y - 28 = 15y + 35
24y - 15y = 35 + 28
9y = 63
y = 7
19.
4(3 – х) – 11 = 7(2х – 5)
12 - 4x - 11 = 14x - 35
1 - 4x = 14x - 35
14x + 4x = 1 + 35
18x = 36
x = 2
20.
96 – (26 + х) = 4
96 - 26 - x = 4
70 - x = 4
x = 70 - 4
x = 66
21.
17– 6а = 3 – 4а
-4a + 6a = 17 - 3
2a = 14
a = 7
22.
4х + (118 – х) = 38 – 5х
4x + 118 - x = 38 - 5x
3x + 118 = 38 - 5x
3x + 5x = 38 - 118
8x = -80
x = -10
23.
7(3у + 5) – 4(5у + 9)= – 2(3у+18)
21y + 35 - 20y - 36 = -6y - 36
y - 1 = -6y - 36
y + 6y = -36 + 1
7y = -35
y = -5
24.
5(3у – 6) – 2(2у + 7) = у + 6
15y - 30 - 4y - 14 = y + 6
11y - 44 = y + 6
11y - y = 6 + 44
10y = 50
y = 5
25.
3(5 – а) + 13 = 4(3а – 8)
15 - 3a + 13 = 12a - 32
28 - 3a = 12a - 32
12a + 3a = 28 + 32
15a = 60
a = 4
35-15= 20 минут
20*60=1200 секунд
ответ 1200 секунд