<s>[INST] Here is a challenging math problem.  I have a line of people waiting outside a small store.  The store has only one cash register that is used by one cashier.  There are already 10 people in line.  Every minute, two people join the line.  Also, every minute, the cashier can process 5 people in the line.  In other words, every minute, the store gains 2 customers, but can do 5.  Since the store can gain 2 but can only do 3 fewer people per minute, what is the length of the time it will take for the cashier to finish checking out the people in the original line.  Note, the first minute, the cashier will be able to check out 5, but the store gains 2, so the net gain to the cashier on the first minute is 3.  In other words, since the store gains 2 customers per minute, and the cashier can check out 5 in the same minute, the cashier does 3 every minute.[/INST]