Question

5x + 9y = -54
2x + y = 20

a.) Find the solution to the system of equations using either substitution of the linear combination method. Show all your work.

I've tried but I can't seem to understand how to do this? Does anybody mind giving me steps on how to do either method?

Answer 1

so lets eliminate y by multiplying the second equation by 9:
5x+9y= -54
(2x+y= 20)9= 18x+9y= 180
So now we have these two equations:
5x + 9y= -54
18x+ 9y= 180
Lets now subtract the second equation from the first:
-13x= - 234
to get x alone lets divide both sides by -13
-13x/-13= -234/-13
x=18
Now we can plug x into either problem:
2(18)+y=20
36+y= 20
Now we subtract 36 from both sides.
y= 20-36
y= -16