There are 20 students. Two monitors are to be selected from 20 students. If one of the student is suffered from the disease and unable to attend a school then, how many ways are there to select a monitor?
1
168
2
171
3
162
4
176
There are 20 students. Two monitors are to be selected from 20 students. If one of the student is suffered from the disease and unable to attend a school then, how many ways are there to select a monitor?