Verified Answer :

You multiply 3 by both m and n.
You get 3m+3n

Answer:

\(3m+3n\)

Step-by-step explanation:

The distributive property is defined as  the multiplication of a number by a sum is equal to the sum of the multiplications of that number by each of the addends:

\((a+b)c=ac+bc\)

Using the previous property:

\(3(m+n)=(3*m)+(3*n)=3m+3n\)