First rewrite each term as:
#3sqrt(16 * 6k) + 2sqrt(36 * 5)#
Next, use this rule for radicals to rewrite each radical:
#sqrt(color(red)(a) * color(blue)(b)) = sqrt(color(red)(a)) * sqrt(color(blue)(b))#
#3sqrt(color(red)(16) * color(blue)(6k)) + 2sqrt(color(red)(36) * color(blue)(5)) =>#
#3sqrt(color(red)(16) * color(blue)(6k)) + 2sqrt(color(red)(36) * color(blue)(5)) =>#
#3sqrt(color(red)(16))sqrt(color(blue)(6k)) + 2sqrt(color(red)(36))sqrt(color(blue)(5)) =>#
#(3 * 4)sqrt(color(blue)(6k)) + (2 * 6)sqrt(color(blue)(5)) =>#
#12sqrt(6k) + 12sqrt(5)#
Now, facture out the common term:
#color(red)(12)sqrt(6k) + color(red)(12)sqrt(5) =>#
#color(red)(12)(sqrt(6k) + sqrt(5))#