Question

Tally Marks	Number of Observations
	________________________

Answer 1

Tally mark is a way by which we can count the occurrence of any data by using a small single line to represent one occurrence of data and cutting four lines by a single line to represent a group of five occurrence.

So, here there are three groups of 5 each and one single line, therefore $5+5+5+1=16$

hence, the solution is $16$