To prove the equivalence of the expressions \( y \cdot 3x \) and \( 3xy \) using the Commutative Property, we can rearrange the multiplication in Expression 1:
\[ y \cdot 3x = 3 \cdot y \cdot x = 3xy. \]
Since multiplication is commutative, the order in which we multiply the numbers does not change the result. Therefore, both expressions are equivalent. This demonstrates that rearranging the factors in a multiplication operation yields the same product.