algebra
posted by desperate! .
You have a bag with 60 black jelly beans and 240 red ones.
a) If you draw one jelly bean out of the bag, find the probability that it is black.
60/300= 1/5
b) If you add 60 black jelly beans to the original bag and draw out a bean, what is the probability that it is black?
120/360= 1/3
c) How many black beans do you need to add to the original bag to double the original probability of drawing a black bean?
d) Write an equation that represents the problem in part (c).
I GOT A AND B JUST NEED C AND D PLEASE?(:

Add x black beans.
Probability of drawing a black bean after adding more black beans
=(60+x)/(300+x)
If that has to be doubled from before (1/5=60/300), then
(60+x)/(300+x)=2*(1/5)
solve for x.