Answer
$(m\times3)7=21m$
Work Step by Step
Show that $(m\times3)7$ is equivalent to $21m$.
$(m\times3)7\longrightarrow$ Use the associative property.
=$m(3\times7)\longrightarrow$ Simplify.
=$m(21)\longrightarrow$ Use the commutative property.
=$21m$