Concept:Use the inclusion-exclusion principle and the formula for probability.Explanation:Total tickets from 51 to 80 are:80−51+1=30Numbers divisible by 3 from 51 to 78:378−51​+1=10Numbers divisible by 5 from 55 to 80:580−55​+1=6Numbers divisible by both 3 and 5 are multiples of 15, from 60 to 75:1575−60​+1=2Favorable outcomes:10+6−2=14Probability:Probability=3014​=157​Answer:157​, i.e., Option C.