"The difference of two problems is 33"--->
"The second is 7 less than 3 times the first"---->
Start with the given system
Plug in into the first equation. In other words, replace each with . Notice we've eliminated the variables. So we now have a simple equation with one unknown.
Combine like terms on the left side
Add 7 to both sides
Combine like terms on the right side
Divide both sides by 2 to isolate x
Divide
Now that we know that , we can plug this into to find