Question

The sum of two numbers is 21. The difference of the two numbers is 3. What are the numbers?​

Answer 1

Answer:

y=9

Step-by-step explanation:

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 3. In other words, x minus y equals 3 and can be written as equation B:

x - y = 3

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

x - y = 3

x = 3 + y

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

x + y = 21

3 + y + y = 21

3 + 2y = 21

2y = 18

y = 9

Now we know y is 9. Which means that we can substitute y for 9 in equation A and solve for x:

x + y = 21

x + 9 = 21

X = 12

Summary: The sum of two numbers is 21 and their difference is 3. What are the two numbers? Answer: 12 and 9 as proven here:

Sum: 12 + 9 = 21

Difference: 12 - 9 = 3

Answer 2

Answer:

Step-by-step explanation:

let the 2 number be x,y

(1)x+y=21

(2)x-y=3

so x=3+y

substituting in equation (1)

3+y+y=21

3+2y=21

2y=21-3=18

y=9

so x=12

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