In find the pattern problems like these, there are almost always an infinite number of possible solutions because we have a finite number of starting values. In this case we don't know what kind of series we're talking about.
One possible solution, probably not the one your teacher is looking for is:
48, 23, 20, 11, 16, 70, ...
On each step add the digits, 2x that value, then 4x, 6x, 8x, and so on, then, lower the value to the next number that isn't divisible by 3.
Need more info, or need to know what kind of problems you were working on in that chapter.