# What does it mean to solve a system of equations by substitution?

##### 1 Answer

I think that this is better explained with an example.

Lets say that we have the linear system

Neither one of these equation can be solved on their own because an equation with more than one unknown value cannot be solved.

We have to eliminate one of the variable by substitution.

We have 2 options. First, pick one of equations and then solve for either

Lets use the first equation and solve for

Now we see that

Make substitution for

Combine like terms

Subtract 17 from both sides

Divide by sides by

Now we can find

Okay, so now we know that

We check our work by substituting those values into the other equation.