On Gabrielle's equations, she multiplied the sum inside the parentheses by the coefficient outside of the parenthesis. This caracterizes the distributive property.
The distributive property is a property of multiplication used in addition and subtraction. By definition, this property states that two or more terms in addition or subtraction with a number are equal to the addition or subtraction of the product of each of the terms with that number.
[tex]a(b+c)=ab+ac[/tex]