Which of the following waves has the largest wave speed?

The displacement of a wave travelling in the $x$ direction is $y = 10^{-4} \sin(600t - 2x + \pi/3) \text{ m}$,where $x$ is in metres and $t$ is in seconds. The speed of the wave is: (in $\text{ m/s}$)

What is a wave equation?

Two waves are represented by the equations $y_1 = A \sin (\omega t + kx + 0.57) \ m$ and $y_2 = A \cos (\omega t + kx) \ m$,where $x$ is in metre and $t$ is in second. What is the phase difference between them?

$A$ plane wave is described by the equation $y = 3 \cos \left( \frac{x}{4} - 10t - \frac{\pi}{2} \right)$. The maximum velocity of the particles of the medium due to this wave is

$A$ person is producing a wave in a string by moving his hand first up and then down. If the frequency is $\frac{1}{8} \, Hz$,then find out the time taken by a particle which is at a distance of $9 \, m$ from the source to move to the lower extreme for the first time in seconds. (Given $\lambda = 24 \, m$)