When you have two variables, you need to equations to determine the values. You provided information fot only 1 equation
(-5, 2)
x + 5y = 10 5y = -x + 10 y = -x/5 + 2 m = -1/5 or .2
7x + 5y 7(3) + 5(2) 21 + 10 = 31
7
(-1, 2)
It equals x+5y simplified
x=0 y=2
(x, y) = (3, 2)
x=(-5y-1)/3
z = -4 x-5 y+2
5y + x = 0 subtract 5y from each side, then x = -5y
X = -2(13 + y) / 3x = 5y / 4 - 1