Answer: 153
Step-by-step explanation:
When we have a group of N elements, the total number of combinations of K elements ( K ≤ N) is:

Where N! = N*(N - 1)*(N - 2)*...*2*1
In this case, we have a group of 18 people (then N = 18) and we want to see how many different combinations of 2 we can make (K = 2).
Using the above equation we get:

There are 153 different ways in which the manager can do this.
The location is 6,0 because if you know the location of A and B you get -3,3 for A and 2,9 for B
The answer would be horizontal reflection because it has been reflected over a horizontal line. Hope this helps :-)
Use Pythagoras theorem:
It can be used in any right triangle