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What is the sum of these mixed numbers 2 1/8 + 4 3/8

Can anyone me with 32,33,36,37,and 40.

Aproduction manager test 10 toothbrushes and finds that their mean lifetime is 450 hours. she then design sales package of this type of toothbrush. it states that the customers can expect the toothbrush to last approximately 460 hours. this is an example of what phase of inferential statistics