In a bag, there are 10 red, 15 green, and 12 blue marbles. if you draw two marbles (without replacing), what is the approximate probability of drawing two different colors?

Probability is the possibility of an event occurring. In this case the marbles are chosen without replacement, therefore the total number of marbles decreases every time a marble is chosen.
The possible outcomes are RG, RR, RB, GG, GR, GB, BB, BG, BR. Thus those that contain different colors are RG,RB,GR,GB,BG,BR
calculation will be (10/37×15/36) +(10/37 × 12/36) + (15/37 ×10/36) + (15/37×12/36) + (12/37 ×15/36) +(12/37×10/36) = 25/37.
Therefore, the probability of choosing different colors (without replacement) is 25/37.

The answer would be b