Условие:

Выпиши уравнения, решением которых является число 7.
15 − x = 8
13 − x = 7
x + 40 = 47
21 − x = 20
14 − x = 7
17 − x = 10
15 − x = 5
16 − x = 9
27 − x = 20

15 − x = 8
x = 7
157 = 8
8 = 8
 
13 − x = 7
x = 6
136 = 7
7 = 7
 
x + 40 = 47
x = 7
7 + 40 = 47
47 = 47
 
21 − x = 20
x = 1
211 = 20
20 = 20
 
14 − x = 7
x = 7
147 = 7
7 = 7
 
17 − x = 10
x = 7
177 = 10
10 = 10
 
15 − x = 5
x = 10
1510 = 5
5 = 5
 
16 − x = 9
x = 7
167 = 9
9 = 9
 
27 − x = 20
x = 7
277 = 20
20 = 20
 
Ответ:
15 − x = 8
x + 40 = 47
14 − x = 7
17 − x = 10
16 − x = 9
27 − x = 20