Since the sensor transmits 3% of the time, it transmits for 3600 * 0.03 seconds each hour.
For the second question, see this thread. Note that the word "transmission" is used in two different senses in the problem, as that thread says. There was an almost identical question in this thread, which used the phrase "for how long can the sensor continue to operate" (intermittently, as I see it) instead of "how long a transmission is this battery capable of powering". This makes more sense because it avoids that ambiguity.
Try to answer the third question yourself and describe any difficulty if you need help.