Please help me with this homework

Simplify a7/a4 a) 1/a3 b)-a/a2 c)a4/a3 d)a3

Interest begins accruing the date of the transaction except for auto loans mortgages credit card cash advances credit card purchases

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.