Official solution
We have,
\[{{{{\left( {27} \right)}^{999}}} \over 7}\]
= \[{{{{\left( {28 - 1} \right)}^{999}}} \over 7}\]
= \[{{28\,\lambda - 1} \over 7}\]
= \[{{28\,\lambda - 7 + 7 - 1} \over \lambda }\]
= \[{{7\left( {4\lambda - 1} \right) + 6} \over 7}\]
\[\therefore\,\,\,\] Remainder = 6