Use PEMDAS
P Parentheses first
E Exponents (ie Powers and Square Roots, etc.)
MD Multiplication and Division (left-to-right)
AS Addition and Subtraction (left-to-right)
[tex] 7-8\div4\cdot(3^2-1)=7-2\cdot(9-1)=7-2\cdot8=7-16=-9 [/tex]
