Simplify :

81 - 15.68 - 4.2

Given expression:

= 81 - 15.68 - 4.2
= 81.00 - 15.68 - 4.20 $\quad$ [Converting into like decimals]
= (81.00) - (15.68 + 4.20) $\quad$ [Rearranging terms]
= 81.00 - 19.88
= 61.12

$\begin{array}{r|r} 15.68 & 81.00 \ +\phantom{0}4.20 & -\phantom{0}19.88 \ \hline 19.88 & 61.12 \ \hline \end{array}$

Hence, the answer is 61.12