Answer
$71$
Work Step by Step
Let the number of girls in band be $x$. Then:
$$x\cdot \frac16=6$$
$$x=6\cdot6=36$$
Let the number of boys in band be $y$. Then:
$$y\cdot \frac27=10$$
$$y=10\cdot\frac72=5\cdot 7=35$$
Total students in band:
$$36+35=71$$
