The equation \( 5x + 3 = x \cdot 5 + 3 \) reflects the Commutative Property of Multiplication.
The Commutative Property of Multiplication states that the order in which two numbers are multiplied does not change the product, i.e., \( a \cdot b = b \cdot a \). In this case, \( 5x \) can be rewritten as \( x \cdot 5 \), demonstrating that the multiplication operation is commutative.
Thus, substituting 1 for \( x \) tests whether the two expressions are equal when evaluating them, confirming that multiplication's order does not affect the outcome.
So, the correct response is:
The Commutative Property of Multiplication.