PEMDAS
P - PARENTHESIS
E - EXPONENTS
M - MULTIPLICATION
D - DIVISION
A - ADDITION
S - SUBTRACTION
So we do that from left to right:
[tex][ 7+(15 -3)/6]\times 3[/tex]
First we do parenthesis:
[tex][ 7+12/6]\times 3[/tex]
Now we have to take care of the next parenthesis. Inside of it is addition and division happening. So we have to do the division first:
[tex][ 7+2]\times 3[/tex]
Now we do the addition:
[tex]9\times 3[/tex]
Now there is only one thing left: Multiplication
[tex]27[/tex]
Your final answer is
[tex]\bf{\huge{\boxed{27}}}[/tex]