The binomial distribution is given by,
P(X=x) =

q = probability of failure = 1-0.2 = 0.8
n = 100
They have asked to find the probability <span>of obtaining a score less than or equal to 12.
</span>∴ P(X≤12) =

where, x = 0,1,2,3,4,5,6,7,8,9,10,11,12
∴ P(X≤12) =

+

+

+

+

+

+

Evaluating each term and adding them you will get,
P(X≤12) = 0.02532833572
This is the required probability.
Slope? rate of change is slop so try that
Since we need to find the number of ways they could enter first, second and third place, (I can't demonstrate, but you should get the idea) take 8, 7 and 6 and multiply them, 5-1 we don't need, we just need 8, 7, and 6, multiply those three numbers and you get 336, there you go, 336 ways to organize all 8 girls in first, second and third place, hope this helps