Substituting 1 for \( x \) in the equation \( 5x + 3 = x \cdot 5 + 3 \) is a test case for the Commutative Property of Multiplication.
In this equation, both expressions \( 5x \) and \( x \cdot 5 \) represent the same product, illustrating that multiplication can be done in any order (i.e., \( ab = ba \)). Thus, it showcases the commutative property of multiplication.