Using PEMDAS
(Parenthesis, Exponents, Multiplication, Division, Addition, Subtraction)
Parenthesis and Multiplication in parenthesis
-7+(7+9x1)x(-1)
-7+(7+9)x(-1)
Parenthesis and Addition in parenthesis
-7+(16)x(-1)
Multiplication
-7-16
Subtraction
-23