The sum of two numbers is 108. the difference of the same numbers is 78. what are the numbers

The sum of two numbers:

x + y = 108

The difference of the same two numbers:

x - y = 78

We can use substitution to figure out x and y:

x - y = 78 can be changed to x = 78 + y

We can plug this into the first equation:

78 + y + y = 108

78 + 2y = 108

2y = 30

y = 15

Now solve for x using any of the two equations. I'll use the first equation since it's easier:

x + 15 = 108

x = 93