Question

Which expression gives the x-coordinate of the solution of the system?

Answer 1

To find the the expression that gives the value of $x$ we are going to proceed as follows: 
$5x+3y=-18$ equation (1)
$2x-4y=-28$ equation (1)

Step 1. solve for $y$ in equation (2)
$2x-4y=-28$
$-4y=-28-2x$
$y= \frac{-28-2x}{-4}$
$y=7+ \frac{1}{2} x$ equation (3)

Step 3. Replace equation (3) in equation (1) and solve for $x$
$5x+3y=-18$
$5x+3(7+ \frac{1}{2} x)=-18$
$5x+21+ \frac{3}{2} x=-18$
$\frac{13}{2} x=-39$
$x= \frac{-39(2)}{(13)}$
$x=-6$

We can conclude that the expression that gives the value of $x$ is: $x=-6$