Подставим вместо неизвестного числа х и решим уравнение.
8 + x = 35 - 20
8 + x = 15
x = 15 - 8
x = 7
8 + 7 = 35 - 20
9 + x = 57 - 40
9 + x = 17
x = 17 - 9
x = 8
9 + 8 = 57 - 40
6 + x = 24 - 10
6 + x = 14
x = 14 - 6
x = 8
6 + 8 = 24 - 10
x - 8 = 36 - 30
x - 8 = 6
x = 6 + 8
x = 14
14 - 8 = 36 - 30
x - 7 = 49 - 43
x - 7 = 6
x = 6 + 7
x = 13
13 - 7 = 49 - 43
x - 5 = 18 - 9
x - 5 = 9
x = 9 + 5
x = 14
14 - 5 = 18 - 9
18 - x = 29 - 20
18 - x = 9
x = 18 - 9
x = 9
18 - 9 = 29 - 20
12 - x = 60 - 56
12 - x = 4
x = 12 - 4
x = 8
12 - 8 = 60 - 56
11 - x = 95 - 90
11 - x = 5
x = 11 - 5
x = 6
11 - 6 = 95 - 90
