Kira is saving money to buy a bike that costs $133 . she has $42 and will save an additional $7 each week. in how many weeks will she have enough money to buy the bike?

(4/5)^7 x 1/5

Step-by-step explanation: This is a geometric probability distribution. The probability of a success is 20% = 1/5 and the probability of a failure is therefore 4/5.

We want to know the probability that Ben is successful on the eight attempt. This means he has failed the first 7 times but succeeds on the 8th try.

So probability is (4/5)^7 x 1/5