Answer:
-5
Explanation:
Okay so 3 is less than 15 so you have to multiply 15 by a negative number so it goes down instead of up, and the reason we multiply is because the b is right next to 15 so that means you multiply.
then you need to find out what multiplied by 3 equalls 15, the answer is 5.
so then you just add the negative sign and vah la you have your answer :D