Răspuns :
15 + 27 = 42
x - 42 = 5
x = 42 + 5
x = 47
x - 42 = 4
x = 46
x - 42 = 3
x = 45
x - 42 = 2
x = 44
x - 42 = 1
x = 43
x - 42 = 5
x = 42 + 5
x = 47
x - 42 = 4
x = 46
x - 42 = 3
x = 45
x - 42 = 2
x = 44
x - 42 = 1
x = 43