Please help i don’t understand any of this.

Ok. No problem. I learned this but I'll improve as I help, you too! So, for the first question, I'm guessing multiply 15 times 420. As goes with the others. And then your answers you came up with is solving for K.

Okay, on part b, round 30 and/or 35, pick one of those that make sense, and then whatever your answer came up with is your answer. Full answer, idk but hopefully I'm right. And PLEASE mark me Brainliest if I'm right. If not or if I am, please star me and comment me, thanks!

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.