... behind the #8 ball, losing ground, running the treadmill, screwed.
This is the same as 3/18 x 21/7, which you can simplify to 1/6 x 3, which is 3/6 also a half. So the answer is 1/2
The question is asking how many combinations of two people can be made from a group of ten people.
Using the formula C(10,2) = 10!/(2! x (10 - 2)! = 10!/(2! x 8!) = 45 handshakes.
A simple way to prove this is each person shakes the hand of 9 other people
10 x 9 = 90 but this counts every handshake from the view of both people involved.
The actual number of handshakes is therefore 90 / 2 = 45
The answer is 7x you just have to ad the numbers in front