Because of PEMDAS, Simplify 15x72 first. That will bring you to 1080. After that we add 6 to the 1080 because you always do Multiplication first. Your answer would be 1086 if you followed PEMDAS correctly.
PEMDAS:
1. Parentheses
2. Exponents
3. Multiplication
4. Division
5. Addition
6. Subtraction
That's the order of operations if you ever want to know what to do first.