To find if the ordered pair is a solution, we substitute (10, -15) into both equations and see if both are true
y = -x -5
-15 = -10 -5
-15 -15
Then we have to check the second equation
4x -8y =4
4(10) -8(-15) = 4
40 +120 = 4
160 does not equal 4 so this is not true
It is a solution to the first equation but not the second so it is not a solution to the system of equations.