Answer
$5.15s$
Work Step by Step
We know that
$t=\frac{v_y-v_{\circ}sin\theta}{-g}$
$t=\frac{-v_{\circ}sin\theta-v_{\circ}sin\theta}{-g}$
$t=\frac{2v_{\circ}sin\theta}{g}$
We plug in the known values to obtain:
$t=\frac{2(9.92)(sin 75.0^{\circ})}{3.72}$
$t=5.15s$
