Life jackets cost $20 and the kayak is $25 an hour
X hours later...
I will rent a kayak and I'll buy one life jacket. I'll pay for the kayak after I'm done.
How many hours did I go kayaking?
Let x= the # of hours you went kayaking. We will use the equation 25x+20= $120 because your total cost was $120. In order to solve this equation you will have to get the x alone on the left side. First, we will do the opposite operation to get rid of the positive 20. Whatever you do to one side, you have to do to the other. Next, you divide both sides by 25 and get x= 4 hours. That is the answer to your question!