Question

Find two numbers whosse sum is 12 and whose difference is 4

Answer 1

x + y = 12
x - y = 4

From the second equation we can see that x = 4 + y

We can plug this into the first one and get:

4 + y + y = 12
4 + 2y = 12
2y = 12-4
2y = 8
y = 4

And then we can plug that into “x” and get that x = 4 + 4, or x=8