First, remove the parenthesis by applying multiplication of like signs. This means that `-(-1)` becomes +1.
And as per order of operation, to simplify start from the left. So, add -13 and 12. Note that when adding numbers with unlike signs, ignore the signs of each number and subtract. The resulting value copies the sign of the larger number.
`=-1 + 1`
Here, -1 is the opposite of 1. As per additive inverse property, the sum of the number and its opposite is zero.