Final answer:
The property illustrated in the equation is the distributive property of multiplication over addition.
Step-by-step explanation:
The property illustrated by the given equation is the distributive property of multiplication over addition.
5(x + 3) = 5x + 15
In this equation, the term 5 is multiplied by each term inside the parentheses, which follows the distributive property. This property states that a number multiplied by the sum of two or more numbers is equal to the sum of the products of that number with each individual term inside the parentheses.