Answer
(a)$31x$.
(b)$31\sqrt{2}$.
Work Step by Step
(a) The given expression is $21x+10x$
Apply the distributive property.
$=(21+10)x$
Simplify.
$=(31)x$
$=31x$.
(b) The given expression is $21\sqrt 2 + 10\sqrt 2$.
Apply the distributive property.
$=(21+10)\sqrt{2}$
Simplify.
$=(31)\sqrt{2}$
$=31\sqrt{2}$.
