You only need to consider the situations where 10 or 11 of the babies are girls, then subtract those probabilities from 1. This will give probability that any other number up to 9 of the babies are girls.
Use binomial theorem.

n = 11
k = 10,11
p = 1/2
So Angel hikes at 2.4 miles per hour. This says that in one hour he hikes 2.4 miles. In 1/3 of an hour then he would hike 1/3 of 2.4 miles, which is 2.4/3, or 0.8.
Let x = number of long sleeve shirts
Let y = number of short sleeve shirts
x + y = 200
x/2 + y/3 = 80
Now solve this pair of simultaneous equations to find x and y.