Find two numbers, if their sum is 3 and their difference is 21.

12 & - 9

Step-by-step explanation:

So you make two equations:

x+y=3 because their sum is 3

x-y=21 because their difference is 21

Now you have to solve one equation, I'll use the first one

x=3-y

Plug in this x into the other equation

x-y=21

(3-y) - y=21

3-2y=21

-2y=18

y=-9

Now solve for the other number

x-9=3

x=12

Your numbers would be 12 and - 9

12 and - 9 that my answers