3-y=24
y=3x solving systems of equations by substitution

{ - 3 - y = 24   ⇒ - y = 24 + 3  .(-1)   ⇒ y = - 24 - 3  ⇒ y = - 27
{ y = 3x

y = 3x
( - 27 ) = 3x
- 27 = 3x
- 27 = x
   3
- 9 = x

S = { - 9 , - 27 }

The answer is a i just took the test