There are 6 people at a diner party. how many handshakes will there be if each person shakes hands with every other guest once

20 hand shakes

Step-by-step explanation:

person 1 shakes hand with 2 3 4 5 and 6, which equals 5

person 2 shakes hand with 3 4 5 and 6, which equals 4

person 3 shakes hand with 4 5 and 6, which equals 3

person 4 shakes hand with 5 and 6, which equals 2

person 5 shakes hand with 6, which equals 1

person 6 already shook hands with everybody so that equals 5

5+4+3+2+1+5=20