Answer:
12.5%
Step-by-step explanation:
you have 7 reds of 14 total.
the 1st marble has 7 of 14 probability of being red
the 2nd has 6 of 13 of being red
the 3rd has 5 of 12 of being red
multiplying this out you have:
(7/14)*(6/13)*(5/12)=210/2184
THAT will condense down to 5/52 or 9.615%
this does assume not placing the balls back in between draws
if you do put them back in between draws you would have 7 of 14 chance each draw
that would give you by multiplying out
(7/14)*(7/14)*(7/14)=343/2744
that condenses to 1 of 8 or 12.5%
