How many nonempty collections of letters can be formed from four as and eight bs?

(hurry! ) which expression is equivalent to the following complex fraction?

Apositive number a or the same number a increased by 50% and then decreased by 50% of the result?

Peter applied to an accounting firm and a consulting firm. he knows that 30% of similarly qualified applicants receive job offers from the accounting firm, while only 20% of similarly qualified applicants receive job offers from the consulting firm. assume that receiving an offer from one firm is independent of receiving an offer from the other. what is the probability that both firms offer peter a job?