The Sum of Two Numbers is 15 and Their Difference is 8

The sum of two numbers is 15 and their difference is 8. 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 15. In other words, x plus y equals 15 and can be written as equation A:

x + y = 15

The difference between x and y is 8. In other words, x minus y equals 8 and can be written as equation B:

x - y = 8

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

x - y = 8
x = 8 + y

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

x + y = 15
8 + y + y = 15
8 + 2y = 15
2y = 7
y = 3.5

Now we know y is 3.5. Which means that we can substitute y for 3.5 in equation A and solve for x:

x + y = 15
x + 3.5 = 15
X = 11.5

Summary: The sum of two numbers is 15 and their difference is 8. What are the two numbers? Answer: 11.5 and 3.5 as proven here:

Sum: 11.5 + 3.5 = 15
Difference: 11.5 - 3.5 = 8

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 15 and Their Difference is 9
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.