In math, brackets are used to group numbers and expressions together and to represent multiplication in expressions that already contain parenthesis. If expressions contain brackets, the numbers within the parenthesis are evaluated first, and then the numbers inside the brackets are evaluated.
For example, 2[10 – 2(6 – 3)] means that first the 6 - 3 in the parenthesis is evaluated giving the expression 2[10 - 2(3)]. The parenthesis represent multiplication, so 2 x 3 is evaluated leaving 2[10 - 6]. Then, the subtraction in the brackets is completed for 2. Finally, the multiplication signified by the brackets is completed for a solution of 8.