First question: no more than three times, that is, 1 time or 2 or 3 times. The probability of one-time dialing is110. If you dialed twice, you must have missed the first time and the second time. That is, 9/10 *1/9 =10, then the probability of dialing three times is 9/10 * 8/9 *18 =10.

So the probability =3/ 10.

The second question seems that parking for one minute doesn't count? This topic is ambiguous.

The third question: this question is a, but you can know that it comes from that box, either a or b, or b is that you are not sure about that box at all (don't ask again, this question is cheating, which means the same thing. . . )