Answer
$f=2Hz$
Work Step by Step
Compare the given equation $y=6.0sin(0.020\pi{x}+4.0\pi{t})$
with $y_{(x,t)}=y_m sin(kx+\omega{t})$
thus $\omega=4.0\pi$
Frequency $f$ can be calculated from the following fromula
$\omega=2\pi{f}$
or $f=\frac{\omega}{2\pi}$
putting the value of $\omega$, we get
$f=\frac{4.0\pi}{2\pi}$
$f=2Hz$
