Answer:
To complete this chart, all you have to do is replace the numbers in the "x" column with the variable "x" in the expressions. Here's what I mean.
For the problem "13-x", replace "x" with the 2. Replace the x with the 2 for the rest of the problems. Then repeat the substitution method (chart is attached so you can see what I mean) with the numbers 4, 6, 8, 10, and 12.
