Can someone please just explain to me and give me the answer

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Find the unit rate for: 75% high-fiber chimp food to 25% high -protein chimp food.

Monitors manufactured by tsi electronics have life spans that have a normal distribution with a standard deviation of 1800 hours and a mean life span of 20,000 hours. if a monitor is selected at random, find the probability that the life span of the monitor will be more than 17,659 hours. round your answer to four decimal places.