solve 2x+4y=10 + 2x+3y=7
You don't want to add the equations because you
would still have two unknowns. Subtract the
second equation from the first equation. That
eliminates the x, and you can solve for y. Then,
plug the y value into either equation to solve for x.
2x + 4y = 10
-(2x + 3y = 7)
--------------------
y = 3
That was easier than expected.
Now, for the x.
2x + 4y = 10
2x + 4(3) = 10
2x + 12 = 10
2x = -2
x = -1
Check:
2x + 3y = 7
2(-1) + 3(3) = 7
-2 + 9 = 7
7 = 7
x is -1, y is 3