Can someone help me out on this? Solve using substitution. x - 4y = 4 6x - 3y = -18

2 Answers

embizze's profile pic

embizze | High School Teacher | (Level 2) Educator Emeritus

Posted on

Given `x-4y=4;6x-3y=-18`

Solve the first equation for `x: x=4y+4`

Substitute this expression for `x` into the second equation:

`6(4y+4)-3y=-18` You now have one equation in one unknown. Solve for `y:`




Then `x=4y+4=4(-2)+4=-4`

So the solution is x=-4,y=-2

Check by plugging back into both equations:

-4-4(-2)=4 check!

6(-4)-3(-2)=-18 check!

acompanioninthetardis's profile pic

acompanioninthetardis | Student, Undergraduate | (Level 1) Valedictorian

Posted on


6x-3y= -18

So just pick a variable that is easy to isolate. Since X in the first equation is all by itself and all we have to do is add 4y to both sides to find its value I'll go with the first equation to solve for X this will then give you


You now have the value of X so you can plug it into the second equation giving you

6 (4y +4) -3y=-18

You then simplify and solve for y. 



Y=-2 you then take this and plug it into the first equation x-4y=4

X-4 (-2)= 4


X= -4

Then plug the x and y values into both equations to double check that the answers match.