the sum of 2 numbers is 30 and their diffrence is 10

Answer 1

Hello London,

If x and y are those numbers:

the sum of 2 numbers is 30 ---> x + y = 30

and their difference is 10 -------> x - y = 10

You can add both equations and you get: x + x + y - y = 40 ----> 2x = 40 ----> x = 20, so one of the two numbers is 20.

Replace x by 20 in either equation. You now have 20 + y = 30, you can solve for y and that will be the other number.