10 + x = 90
x = 90 - 10
x = 80
20 - x = 5
x = 20 - 5
x = 15
10 + x = 90
x = 90 - 10
x = 80
20 - x = 5
x = 20 - 5
x = 15
10 + x = 90
x = 90 - 10
x = 80
20 - x = 5
x = 20 - 5
x = 15
10 + x = 90
x = 90 - 10
x = 80
20 - x = 5
x = 20 - 5
x = 15
10 + x = 90
x = 90 - 10
x = 80
20 - x = 5
x = 20 - 5
x = 15
10 + x = 90
x = 90 - 10
x =80
20 - x = 5
x = 20 - 5
x = 15
10 + x = 90
x = 90 - 10
x = 80
20 - x = 5
x = 20 - 5
x = 15