Brackets have the highest priority in BIDMAS, and are used to change the order in which calculations are carried out.
Perform calculations within brackets first.
Add brackets to this expression to make it correct: 5 + 3 x 3 = 24.
Add the 5 and 3 before the multiply. To make that happen, put brackets around the 5 and the 3.
Without the brackets, the answer is 14.
Answer: (5 + 3) x 3 = 24
Re-write this expression, putting brackets in the correct place: 12 - 6 x 2 + 2 = 24.
Following BIDMAS without brackets gives an answer of -2.
Put the the brackets in first:
(12 - 6) = 6 and
(2 x 2) = 4
6 x 4 = 24
Answer: (12 - 6) x (2 + 2) = 24.
See also Brackets in Algebra