What does -40x-7y=-5 equal to find y

The values x and y are determined when we use the substitution method.

y = x + 5

Apply eh value of y into the equation to solve for x. 

3x + y = 25

3x + x + 5 = 25

Combine like terms

3x + x = 4x

4x + 5 = 25
      -5     -5                               4x = 20

                                                 4x/4 = 20/4
                                                 x = 20/4 
                                                  x= 5

Now we know the value of x, and we need to solve for y.

y = x + 5
y = 5 + 5
y = 10
10 = 10

Now we know both of these values.

x = 5
y = 10