The value of

(c) We have, $\sqrt{248+\sqrt{52+\sqrt{144}}}$

$=\sqrt{248+\sqrt{52+12}}$               $[\because$ square root of $144=12]$

$=\sqrt{248+\sqrt{64}}$

$=\sqrt{248+8}$                                 $[\because$ square root of $64=8]$

$=\sqrt{256}=16$                               $[\because$ square root of $256=16]$