How many solutions does this system of equation have −3x+7y=10 −3x+7y=−8

-3x + 7y = 10
-3x + 7y = -8

If you were to solve this system using elimination, you'd first multiply the bottom equation by -1 to get opposite x- and y-terms, like so:

-1(-3x + 7y = -8)
       3x - 7y = 8

Now you can add the equations together.

    -3x + 7y = 10
      3x - 7y = 8
+
       0  -  0  = 18
               0 ≠ 18

As we know, zero is not equal to 18, so this system has no solutions.

The correct answer is -20y