[tex]54_{10}[/tex]
Explanation:
[tex]\begin{gathered} 86_6\text{ to base 10} \\ \\ 86_6\text{ = 8 }\times6^1\text{ + 6 }\times6^0 \end{gathered}[/tex][tex]\begin{gathered} 86_6\text{ = 8}\times6\text{ + 6}\times1 \\ 86_6\text{ = 48 + 6} \end{gathered}[/tex][tex]\begin{gathered} 86_6\text{ = 54} \\ To\text{ base 10:} \\ 54_{10} \end{gathered}[/tex]
