Kay walks upstairs to make her legs stronger. Every day at work, she walks up 9 flights of stairs. If there are 13 steps in 1 flight of stairs, how many steps does Kay climb in 5 days at work? the answer is 585

On a string instrument, the length of a string varies inversely as the frequency of its vibrations. an 11-inch string has a frequency of 400 cylces per second. find the frequency of a 10-icnch string.

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?