The probability of event A happening is 3/15 chance. This is because there are 15 coins in total but only 3 dimes. The probability of B happening given A just happened ( given a dime was picked), the chance of getting another dime is 2/14 chance because a dime was already chosen so there is one less coin (hence why it is 14 instead of 15) and now there are 2 dimes left. Thus, the answer is 1/7.