http://www.aaamath.com/pro74bx2.htm (these website helped me learn how to do it)
The anwser is zero because...
There are four properties involving multiplication that will help make problems easier to solve. They are the commutative, associative, multiplicative identity and distributive properties.
Commutative property: When two numbers are multiplied together, the product is the same regardless of the order of the multiplicands. For example 4 * 2 = 2 * 4
Associative Property: When three or more numbers are multiplied, the product is the same regardless of the grouping of the factors. For example (2 * 3) * 4 = 2 * (3 * 4)
Multiplicative Identity Property: The product of any number and one is that number. For example 5 * 1 = 5.
Distributive property: The sum of two numbers times a third number is equal to the sum of each addend times the third number. For example 4 * (6 + 3) = 4*6 + 4*3
since it none of these it has to be zero :)
properties of adtition: