Substituting 1 for \( x \) in the equation \( 5x + 3 = x \cdot 5 + 3 \) tests the properties of addition and multiplication. In this case, since the equation simplifies to demonstrate that both sides are equal regardless of the order of the terms or factors, it aligns with the Commutative Property of Multiplication.
Thus, the correct response is:
The Commutative Property of Multiplication