How to answer this? : <p>Two persons are studying for a test.</p>

<p>X’s chances of getting a “B” are 80%. Y’s chances of getting a “B” are 90%.</p>

<p>The probability of at least one of them getting a “B” is 91%.</p>

<p>a. What is the probability that only X gets a “B”?</p>

<p>b. What is the probability that only Y gets a “B”?</p>

<p>c. What is the probability that both won’t get a “B”?</p>
