I don’t understand this

Do, h = (7, 9) (14, 18) the scale factor is

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.

1/2+1/6-3/4 simplify the given expression leaving the answer in improper fraction form.