in order to solve this, use PEMDAS (parentheses, exponents, multiplication, division, addition, subtraction). when solving PEMDAS, you go left to right through the equation for each letter.
5+3-(8-9)1
= 5 + 3 - (-1)1
= 5 + 3 - (-1)
= 5 + 3 - -1
= 5 + 3 + 1
= 9