Question

Solve by elimination 5x+4y = 12 3x - 3y = 18 Please help solve and provide steps.

Answer 1

5x + 4y = 12   ⇒   3(5x + 4y = 12)   ⇒   15x + 12y = 36

3x - 3y = 18   ⇒    4(3x - 3y = 18)   ⇒   12x - 12y =  72  

                                                              27x         = 108

                                                              $\frac{27x}{27}$   =  $\frac{108}{27}$

                                                                   x        =   4

5x + 4y = 12   ⇒   5(4) + 4y = 12   ⇒  20 + 4y = 12   ⇒   4y = -8   ⇒   y = -2

Answer: x = 4, y = -2

Answer 2

First you solve for y.
5x+ y= 12 so Y= 12-5x
And plug it into the next equation
3x- 3(12-5x) = 18
Distribute
3x-36+15x=18
Add 36 to both sides
3x+ 15x= 54
18x= 54 ... divide
x= 3
And you can plug in x to solve for Y
5(3) + y = 12
15+ y = 12 ...subtract 15 from both sides
y= -3