1. Solve this system by substitution.
(y = 3x + 27
y = 4x + 18
2. Solve this system by elimination
(-2x - 4y = -4
2x - 5y = 40
4. Solve this system by substitution
-6x + y = 18
-3x+6y= -24
5. Solve this system by elimination
9x + 21y = 15
-10x + 21y = -61