what is the answer to this systems of equations by substitution

8x - 10y  =  -8

y  =  8

 

Look at the first equation.

 

8x - 10y  =  -8         Now, since  y = 8 , we can replace  " y "  in this equation with  " 8 " .

 

8x - 10(8)  =  -8

                               And 10(8) = 80 .

8x - 80  =  -8

                               Add  80  to both sides of the equation.

8x  =  -8 + 80

8x  =  72

                               Divide both sides of the equation by  8 .

x  =  72/8

x  =  9

 

So the solutions are   x = 9   and   y = 8 .