Answer :
That's the Distributive Property
You multiply whatever is outside of the parenthesis with everything in the parenthesis. That's why when you multiply a with everything in the parenthesis (b + c), it becomes a*b + a*c.
You multiply whatever is outside of the parenthesis with everything in the parenthesis. That's why when you multiply a with everything in the parenthesis (b + c), it becomes a*b + a*c.