divide and write the quotient as a mixed number: 16/5 i don't get it.

A fraction is basically a division problem.  Think about 1/4.  This fraction represents 1 whole divided into 4 pieces.

So, in this problem, the first step is to divide 16 by 5.  It will go in 3 times, with a remainder of 1.

The problem says the answer must be in the form of a mixed number -- that is, a whole number and a fraction.

The remainder in division can be expressed as a fraction:  remainder/divisor.   In this case, the remainder is 1/5.

So, the answer is 3 1/5.