HELPP probability marbles

Question

Given that a box has 3 blue marbles, 2 red marbles, and 4 yellow marbles, use the probability formulas to answer the following questions. Reduce all fractions. Use / as the fraction bar and do not use any spaces. 

P(____)

What's the probability for drawing a yellow marble, given that a red marble was drawn on the first draw and not replaced? 

Answer 1

There are 9 total marbles, 2 red ones and 4 yellow ones.

One red one is drawn, leaving 8 total marbles and still 4 yellow ones

So probability is 4/8 = 1/2 that a yellow one will be drawn on the next pick.