# How do you simplify 3(5+sqrt21)?

$3 \left(5 + \sqrt{21}\right) = 15 + 3 \sqrt{21}$
$3 \left(5 + \sqrt{21}\right)$
Apply the distributive property $a \left(b + c\right) = a b + a c$.
$15 + 3 \sqrt{21}$