If you subtract 16 from my number and multiply the difference by -3 the result is -57 what is my number

Standard deviation of 19,29,21,22,23

An office supply company conducted a survey before marketing a new paper shredder designed for home use. in the survey, 80 % of the people who tried the shredder were satisfied with it. because of this high satisfaction rate, the company decided to market the new shredder. assume that 80 % of all people are satisfied with this shredder. during a certain month, 100 customers bought this shredder. find the probability that of these 100 customers, the number who are satisfied is 69 or fewer.

The answer is 7.2 how would you put this as money