Four notebooks cost $4.40. how many notebooks can you buy for $6.60?

Olivia uses the work below to determine 55% of 720 which explains the error in olivia’s solution

Ajar of gumballs contains 4 reds, 2 greens, and 6 blues. what is the probability of getting two blues in a row without replacement?

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'