Verified Answer :

altavistard

You know how to add and subtract, so why not do what you already know how to do?  What is 3 - 6?  If you get -3, then you've already solved half this problem.

Next, what happens if you combine -4.2x and 2.25x?  Line them up and combine (add or subtract) them vertically.  Is this addition or subtraction?

Write out your two results.  You will obtain a negative term in x and a negative constant term.