Question

Find the value of two numbers if their sum is 12 and their diffference is 4.

Answer 1

8 and 4

Answer 2

Set up two equations and solve.
x+y=12
x-y=4

Solve for y in one:
y=12-x

Plug that into the other equation:
x-(12-x)=4
x-12+x=4
2x-12=4
2x=16
x=8

Then plug x into one of the equations you solved for y:
y=12-8
y=4

Soooooo, the two numbers are 8 and 4.