What is the difference between 68.5 and 0.685?

Converting the given decimals into like decimals, we have to subtract 0.685 from 68.500.

Subtracting columnwise, we get:

$\begin{array}{r} 68.500 \ -\phantom{0}0.685 \ \hline 67.815 \ \hline \end{array}$

Hence, the answer is 67.815