The answer is simply -13.
This is because of the BODMAS rule. BODMAS rule means in an equation that contains brackets, division, multiplication, addition and subtraction we first solve the brackets and then similarly go in order.
In this case we first solve multiplication so it becomes 3-18+2. As now we got only addition and subtraction it is a rule that we go from left to right.
So finally 3-18+2 becomes -15+2 and then -13 finally.