There are 3 yellow cars out of 2+7+3 = 12 total. The probability of selecting yellow is therefore 3/12. We can reduce this, but the answer choices decide not to, so we'll do the same.
After picking a yellow car, we have 12-1 = 11 left over. The amount of blue cars do not go down (because we haven't selected it yet). There are 7 blue cars out of the 11 total, so the probability of picking blue for this case is 7/11
Multiply the two fractions to get (3/12)*(7/11) which is a shorthand way of writing "3 over 12 multiplied by 7 over 11".