What is the apparent solution to the system of equations? y=−x+2y=4x+7

Next time you share two equations, write one equation per line, or separate the two equations with a comma, OK?

y=−x+2y=4x+7   NO

y=−x+2               YES
y=4x+7           

Multiply the first equation by 4, obtaining:              4y = -4x + 8
Add the 2nd equation to this result:                          y = 4x  + 7
                                                                             
                                                                                 5y = 15, and y = 3

Then, using the first equation, determine x:

y = 3 = -x + 2
       1 = -x, so x = -1

The solution is (-1, 3)

She should use 12/3 to measure