Answer:
a) P(2)=0.270
b) P(X>3)=0.605
c) P=0.410
Step-by-step explanation:
We know that customers arrive at a grocery store at an average of 2.1 per minute. We use the Poisson distribution:

a) In this case: 

Therefore, the probability is P(2)=0.270.
b) In this case: 

Therefore, the probability is P(X>3)=0.605.
c) We know that two customers came in in the first minute. That is why we calculate the probability of at least 5 customers entering the other 2 minutes.
In this case: 

Therefore, the probability is P=0.410.
You would multiply by 1.2 for example if you wanted to find 120% of 100 you would multiply by 1.2 and get 120
3(3x9)
3x3=9
3x9=27
9+27=36