Question

To multiply a monomial by a polynomial, do you use the Associative or Distributive Property.

Answer 1

You would use the distributive property.

Answer 2

You use the Distributive Property.
Example: 

monomial - 2
polynomial- 3x+4

Use the distributive property: 
2(3x+4)
=[(2)(3x)] +[(2)(4)]
=6x+8