Divide 21 by 13, and you get 1, remainder 8. "Bring down" the 6, and now you're dividing 86 by 13; you get 6, remainder 8, so the answer is 16, remainder 8, or 16 8/13.
54 ÷ 4 = 13 remainder 2
30.8571
9
216
3
0.0185
4
31 divided dy 216 = 0.14351851851851852
36
9.8182
54
216 divided by 72 is three.