speed of wave y = a sin `(omega - 2pix/lambda)` is given by

Explanation

The given equation is
y = `asin(wt - (2pix)/lamda)` …..(1)
The standard equation is
y = asin(wt - kx) ……(2)
comparing (1) and (2) `k = (2pi)/lamda, k = w/v`
`thereforew/v = (2pi)/lamda`
`therefore v = (lamda w)/2pi)`