There are 7 marbles in the bag.
The probability of drawing a pink one is (3/7) .
Then you have 1 pink one, and there are 6 marbles in the bag.
The probability of drawing a pink one is (2/6) .
Then you have 2 pink ones, and there are 5 marbles in the bag.
The probability of drawing a pink one is (1/5) .
The probability of all 3 draws being successful is
(3/7) (2/6) (1/5) = 6/210 = 1/35 = about 2.86% (rounded)
