The Sum of Two Numbers is 18 and Their Difference is 7

The sum of two numbers is 18 and their difference is 7. 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 18. In other words, x plus y equals 18 and can be written as equation A:

x + y = 18

The difference between x and y is 7. In other words, x minus y equals 7 and can be written as equation B:

x - y = 7

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

x - y = 7
x = 7 + y

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

x + y = 18
7 + y + y = 18
7 + 2y = 18
2y = 11
y = 5.5

Now we know y is 5.5. Which means that we can substitute y for 5.5 in equation A and solve for x:

x + y = 18
x + 5.5 = 18
X = 12.5

Summary: The sum of two numbers is 18 and their difference is 7. What are the two numbers? Answer: 12.5 and 5.5 as proven here:

Sum: 12.5 + 5.5 = 18
Difference: 12.5 - 5.5 = 7

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The Sum of Two Numbers is 18 and Their Difference is 8
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