Define x :
Let one of the number be x
The other number is x + 1
Solve x:
the sum is 139
x + (x + 1) = 139
x + x + 1 = 139
2x + 1 = 139
2x = 138
x = 69
Find the numbers:
First number = x = 69
Second number = x + 1 = 69 + 1 = 70
Answer: The numbers are 69 and 70