Question

Find two numbers whose sum is 42 and whose difference is 16.

Answer 1

a + b = 42
a - b = 16 ==> a = b + 16

b + 16 + b = 42
2b + 16 = 42
2b = 42 - 16
2b = 26
b = 26/2
b = 13 <===

a = b + 16
a = 13 + 16
a = 29 <===