The rule in the order of operations is that addition and subtraction are carried out left to right. Whichever operation is leftmost is executed first. Of course the associative and commutative properties of addition mean that you can rearrange the operands to suit yourself. (Keep the sign with the number when doing so.) Example -1 + 2 - 3 + 4 - 5 = 1 - 3 + 4 - 5 (perform the left-most addition first, according to the order of operations) = -2 + 4 - 5 = 2 - 5 = -3 Alternatively -1 + 2 - 3 + 4 - 5 = (2 + 4) - (1 + 3 + 5) (regroup using commutative, associative, and distributive properties) = 6 - (4 + 5) (addition according to the order of operations) = 6 - 9 (finish using the order of operations) = -3
