I have an even distribution of age in the range $[Ab)$[Ab)$[ab)$[ab)$ with $ a = $ 42 and $ b = $ 78

So, the probability that a person walks in a bank located between $ 50 $ and $ 70 years would be $ frac {70-50} {78-42} $, right?

But I'm struggling with this problem where I'm supposed to find

- The probability that 3 out of 7 customers in the bank are between $ 50 $ and $ 70 years of age
- The probability that the $ 7 customer entering the bank is between $ 50 $ and $ 70 years of age
- The probability that the $ 7 customer entering the bank is also the 3rd customer between $ 50 $ and $ 70 years of age

For $ 1. $is it right $ frac {20} { binom {7} {3}} $?

And for $ 2. $ and $ 3. $I am a little lost so I need help on them