Question

Use addition to solve the linear system of equations. Include all of your work in your final answer. 1

-x-y=5
x+2y=5

Answer 1

We will need to make both equations equal to the same subject, in this case we will make them both equal to x:

-x-y=5
-y-5=x

x+2y=5
x=5-2y

Now because they are both equal to x, they are therefore equal to each other:

-y-5=5-2y

Now we solve for y:

y=10

Now that we have y, we can substitute it back into either original equation to get x (always use the easier one):

-x-10=5
-15=x

I hope this counts as using addition.