Follow PEMDAS. Parentheses: 16+a, which is 18. There are no exponents so move on to multiplication. 6b. B is equal to 3, and 6x3 is 18. Next, division. 18/3 is 6. Now do addition so add together 18+6 which is 24.
Okay so the zero property of multiplication is anything times zero equals zero, so just use a number, multiply it times zero, and show what it equals (which is zero) explain that it shows the property because the variable is multiplied times zero.