Sadie has $1 worth of nickels and dimes. She has twice as many nickels as dimes. Write a system of equations that could be used to determine the number of nickels and the number of dimes that Sadie has. Define the variables that you use to write the system.

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?