The brackets in mathematical expressions are used to show the order of operations. Brackets can drastically alter the result of an expression. For example, if you were figuring out the amount of money you had if you started with £6 and spent £1.30 on one purchase and £2 on another and you wrote £6 - £1.30 + £2, you would get £7, more than you started with and obviously incorrect. Instead, use brackets as in the expression £6 - [$2 + £2] to find the correct answer of £2.
Order of Operations
When there are brackets in the expression, perform the operations in the brackets first. For example, given the expression 10 - [2 + 4], simplify 2 + 4 to get 6, so the expression would then be 10 - 6 with a solution of 4. If there are multiple addition and subtraction problems within the brackets, proceed from left to right. For example, if the expression was 15 + [3 - 5 + 4], subtract 5 from 3 to get -2, then add 4 to get 2 so your expression would then be 15 + 2, or 17.
Adding to Brackets
If you have an addition sign in front of the brackets, disregard the bracket when you are simplifying the expression. For example, if you had the expression 3 + [12 - 4], it would not matter whether you added 3 plus 12 and then subtracted 4 or if you subtracted 4 from 12 and added 3 to the result, because either way you will get 11.
If you are subtracting the result of expressions within brackets, distribute the subtraction sign to each of the numbers within the brackets. For example, in the expression 14 - [7 + 2], distribute the negative sign to get 14 - 7 - 2. Solving the expression from left to right will give you an answer of 5.