Question

Jade had the following system of equations to help her with a physics problem, but she only needed to know what the sum of x and y is.
2x+3y=12
2x-y=4
What is the value of x+y?

Answer 1

From the second:

2x-y=4

x=(4+y)/2 and applying this to first:

4+y+3y=12

4y+4=12

4y=8

y=2 and since x=(4+y)/2, x=3 so 

x+y=2+3=5