Using the substitution method, Zack is solving the following system of equations algebraically:
y + 3x = -4
2x – 3y=-21
Which equivalent equation could Zack use?
1) 2(–3x – 4) + 3x =-21
3) 2x – 3(–3x – 4)=-21
2) 2(3x – 4) + 3x = -21
4) 2x – 3(3x – 4) = -21