Answer
The direction of propagation of the wave is in the $'-x '$ direction.
Work Step by Step
We determine the direction from phase i.e. $(kx+_-\omega{t})$. In the current scenario, it is $(0.020\pi{x}+4.0\pi{t})$ which represents $(kx+\omega{t})$. As the given equation uses a $'+'$ sign for phase, the direction of propagation of wave is along the $'-x'$ axis.
