Question 741493
Solve the second equation for x


x-3y=7


x=7+3y


Then plug this into the first equation 


2x+4y=-6


2(7+3y)+4y=-6 ... replace x with 7+3y


Notice how this is now an equation with a single variable (y). Solve this for y. Then use this solution to find x. I'll let you finish up.