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How do you determine if an ordered pair is a solution to a given equation?

Ian is in training for a national hot dog eating contest on the 4th of july. on his first day of training, he eats 4 hot dogs. each day, he plans to eat 110% of the number of hot dogs he ate the previous day. write an explicit formula that could be used to find the number of hot dogs ian will eat on any particular day.

The difference of three and the reciprocal of a number is equal to the quotient of 20 and the number. find the number.