Answer:
Step-by-step explanation:
you know the value of y.
so substitute it into the first equation
-4x + 7(3x+15) = 20
now solve for x
-4x +21x + 105 = 20
17x + 105 =20
17x = -85
x = -5
now put the value of x into the y equation.
y = 3(-5) +15
y = -15 + 15
y = 0
