The Sum of Two Numbers is 77 and Their Difference is 99

The sum of two numbers is 77 and their difference is 99. What are the two numbers? Let's start by calling the two numbers we are looking for x and y.

The sum of x and y is 77. In other words, x plus y equals 77 and can be written as equation A:

x + y = 77

The difference between x and y is 99. In other words, x minus y equals 99 and can be written as equation B:

x - y = 99

Now solve equation B for x to get the revised equation B:

x - y = 99
x = 99 + y

Then substitute x in equation A from the revised equation B and then solve for y:

x + y = 77
99 + y + y = 77
99 + 2y = 77
2y = -22
y = -11

Now we know y is -11. Which means that we can substitute y for -11 in equation A and solve for x:

x + y = 77
x + -11 = 77
X = 88

Summary: The sum of two numbers is 77 and their difference is 99. What are the two numbers? Answer: 88 and -11 as proven here:

Sum: 88 + -11 = 77
Difference: 88 - -11 = 99

Sum Difference Calculator
Do you want the answer to a similar problem? Enter the sum and difference here to find the two numbers:

The Sum of Two Numbers is 78 and Their Difference is 1
Using what you learned on this page, try to figure out the next problem on our list and then go here to check the answer.