Verify Whether $1 + 2 + 3 + \ldots + n = \frac { n } { 2 } ( n + 1 )$

Multiple Choice

Verify whether $1 + 2 + 3 + \ldots + n = \frac { n } { 2 } ( n + 1 )$ is true for $n = 7$

A) yes
B) no