Answer:
Step-by-step explanation:
formula for area of a parallelogram is 
where 
stands for base and 
stands for height.
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 is 7.5 because you divide the circumference in half. Half of 15 is 7.5.
-0.25 is the slope between those two points.
