Question

if 15 person handshake with eatchouther then how many person handshake ?

Answer 1

its simple ur answer is 15*14 =210

Answer 2

formula for number of handshakes in a group of n people

$= \frac{n(n - 1)}{2} \\ here \: n = 15 \\ = \frac{15 \times 14}{2} \\ = \frac{210}{2} \\ = 105$

therefore if 15 people handshake among themselves then 105 handshakes are possible