Question

What is the y-coordinate for the solution of the system of equations below? 7y+5x=19 3y+5x=7

Answer 1

I would go about solving this by elimination because the x variables are already the same so all you would have to do is change one equation to the opposite signs and add them, so it would look like:

7y + 5x = 19
+ -3y - 5x = -7
-------------------
4y=12
y=3

Answer 2

7y + 5x = 19 ⇒ 21y + 15x = 57
3y + 5x = 7   ⇒ 21y + 21x = 49
                                   -6x = 8
                                    -6   -6
                                     x = -1 1/3
                           7y + 5x = 19
                 7y + 5(-1 1/3) = 19
                       7y - 6 2/3 = 19
                            +6 2/3    +6 2/3
                                  7y = 25 2/3
                                   7          7
                                    y = 3 2/3
                              (x, y) = (-1 1/3, 3 2/3)