Add:

6.9, 23.84

Maximum number of decimal places in given decimals is 2. So, we convert them into like decimals, each having 2 places of decimal, by annexing zeros.

$\begin{array}{r} 6.90 \ +\phantom{0}23.84 \ \hline 30.74 \ \hline \end{array}$

Hence, the sum is 30.74