Marbles probability question

Question

I have a math test tomorrow and DEFINITELY need to learn how to solve a question like this. heres the question below.

 

A jar contains 29 green marbles, 16 red marbles, 24 blue marbles, 20 yellow marbles, 21 white marbles, and 24 purple marbles. One marble is selected at random. Find the probability the selected marble is not red, given that it is not blue.

Answer 1

If the marble is not blue, then the total of eligible marbles from which to choose excludes the # of blue marbles.

 

Add up marbles of all colors except blue. 

 

P(red|choice was not blue) = 16 divided by the above blue-less total.

Answer 2

red is 16/134, not red is (134-16) /134

blue is 24/134, not blue is (134-24)/134