51 cities were surveyed to determine sports teams. 19 had soccer, 15 had rugby, 12 had volleyball, 9 had soccer and rugby, 8 had soccer and volleyball, 6 had rugby and volleyball. 3 had all three. How many only had a rugby team?

a) one student is chosen from classroom a, then a student is chosen from classroom b.  

step-by-step explanation:

independent events are ones in which the probability of one event does not affect the probability of the second event.

one student is chosen from classroom a; this does not affect the chances of choosing a student from classroom b.   this makes these independent events.

when one card is chosen from a standard deck and then set aside before a second card is chosen, the probability of the second card being chosen changes.   this makes them dependent events.

when one student is chosen from classroom a and then a second student is chosen from classroom a, the probability of choosing the second student changes.   this makes them dependent events.

when a letter is chosen from the alphabet and then a second letter is chosen, the probability of choosing the second letter changes.   this makes them dependent events.

2nd one in the first row is correct

the answer i believe is 27 units.

step-by-step explanation: