First we subtract the given values from 15.6 to find out how much she has left when she buys the folders.
15.6-3.4-1.98-8.6=1.62
She has $1.62 remaining and she buy two identical folders. That means both were at the same price. So we just need to divide by two to find the cost of each individual folder.
It would take the faucet 18 hours to fill the tank because 18/12=1.5. That means it will be 1.5 times slower to fill the tank up with the hose on. 1.5*12=18.
64 is the starting number because it is given, and x represents how many rounds there are. 1/4 represents how much of the teams remain after each round.
