An equation in the form of slope intercept is written as y=mx+b. That means that we need to get y positive, which we can do by adding 3y to each side, and then subtracting 3 from each side to get y by itself. Doing all of these steps, the equation becomes 3y=5x-3. But, we're not done because we still need to get y equal to one, which we can do by dividing each side of the equation by 3. This makes the equation become y=5/3x-1.
The graph of the equation looks like this:
You could use many methods to find the answer to this problem, but I am going to use the most efficient one I know.
18f+15(4f)=156
F is for fins. We should now solve the equation.
18f+60f=156
78f=156
156÷78=2
So fins cost 2 dollars. Now, we know snorkels cost four times the amount of fins. Four times 2 is eight. So the snorkels cost $8 to rent. Let's check our math.
15(8) + 18(2)
120+36=156
So it cost $8 to rent a snorkel.
The answer to your question is 7,600 fish