A bag had 3 pink marbles and 4 purple marbles find the probability of selecting 3 pink marbles without replacement

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)