Personally I have been taught the BODMAS rule from childhood. So basically you solve anything inside the bracket, orders of magnitude, division, multiplication, addition and subtraction respectively.
The problem we have is:
48÷2(3+9)
Applying the above rule we first do the operation inside the bracket:
3+9=12
Keeping in mind that the relation between anything inside the bracket with anything outside it is just a multiplication (example: 3(5) is the same as 3*5 which both equal 15), we perform the division in this problem:
48÷2=24
Finally we perform the bracket multiplication:
24(12)=288
So to show everything in order:
48÷2(3+9)
=48÷2(12)
=24(12)
=288
Just as an extra, typing the exact equation as it is given into excel gives 288 as well. Of course that's how excel was programmed anyway.
Essentially this is a simple notation problem and how you approach it. Problems like these are very contextual.
