How do you solve the system of linear equations #2y+6=x# and #3y+10=x#?
1 Answer
Since x is already isolated in both equations we can easily solve for y by substitution.
Explanation:
Now solve for x by substituting 4 for y in either one of the equations.
The solution set is
Here are a few of the most fundamental rules for solving systems of equations by substitution.

Always solve for the easiest variable in the equation. For example, in
#6x + 3y = 9# , it would be easiest to solve for y because you don't end up with fractions, which can become long and tricky to work with. 
Always only replace the value of x or y in the equation. Don't get rid of any coefficients x or y may have. Example:
If you want to substitute 2x + 3 = y into
#4x  2(2x + 3) = 3
You would then distribute and then solve.
Practice exercises:
 Solve the following linear systems of equations by substitution.
a).
b).
Good luck!