First you should do the sum in the first brackets, then to do the sum in the second brackets and then the third bracket. Then you should do the sum with 'of'. 'Of' means multiplication and then you will do the division parts. Then to do the part of multiplication. You can say that multiplication and 'of' are same. Then you will do the part of addition and then you will do the part of subtraction. Doing like this you will not have any mistake and it is also the easiest and shortest method of simplification.