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.
Practice, practice & practice.
Answer:
So the number of ways of choosing two distinct letters at a time is (42)=6. We can then add the duplicate pairs which are O,O and N,N to give a total of 8 possible pairs.
64
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