Условие:

☐ + 15 = 20
15 − ☐ = 8
☐ − 9 = 7
90 + ☐ = 100
8 + ☐ = 14
☐ − 8 = 14

5 + 15 = 20
157 = 8
169 = 7
90 + 10 = 100
8 + 6 = 14
228 = 14