The Sum of Two Numbers is 21 and Their Difference is 2

The sum of two numbers is 21 and their difference is 2. 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 21. In other words, x plus y equals 21 and can be written as equation A:

x + y = 21

The difference between x and y is 2. In other words, x minus y equals 2 and can be written as equation B:

x - y = 2

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

x - y = 2
x = 2 + y

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

x + y = 21
2 + y + y = 21
2 + 2y = 21
2y = 19
y = 9.5

Now we know y is 9.5. Which means that we can substitute y for 9.5 in equation A and solve for x:

x + y = 21
x + 9.5 = 21
X = 11.5

Summary: The sum of two numbers is 21 and their difference is 2. What are the two numbers? Answer: 11.5 and 9.5 as proven here:

Sum: 11.5 + 9.5 = 21
Difference: 11.5 - 9.5 = 2

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The Sum of Two Numbers is 21 and Their Difference is 3
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