We want to estimate the following sum
[tex]15.12+78.88[/tex]To do so, we just need to get each term of the sum to the closest multiple of 10.
[tex]\begin{gathered} 15.12\approx20 \\ 78.88\approx80 \end{gathered}[/tex]Then, we have
[tex]15.12+78.88\approx20+80=100[/tex]The answer is option D.
