Hey, I am in MAT270 and I can't find how to do this problem anywhere in my book, can someone help me out?

I am going to post a similar problem because I would like to figure out how to do this by the steps taken to find the answer to the similar problem.

"Use the position function f(t) meters to find the velocity at time t=a seconds."

√(t+16) [square root of (t+16)], (a) a=0; (b) a=2