Answer :

Problem:  161.7 ÷ 7 =

161.7 rounded to the tenths place is 162.
7 rounded to the ones place is 10. So divide 162 by 10.

162 ÷ 10 = 16.2    
16.2 rounded to the tenths place is 16.

Answer:

So the answer of the estimation is 16.