How do you write 6.12 as a fraction

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

Need asap. solve for the following inequality

There are three bags: a (contains 2 white and 4 red balls), b (8 white, 4 red) and c (1 white 3 red). you select one ball at random from each bag, observe that exactly two are white, but forget which ball came from which bag. what is the probability that you selected a white ball from bag a?