PEMDAS (right to left) (Parentheses, exponents, Multiplication/Division, Addition/Subtraction) or Please Excuse My Dear Aunt Sally is what I was taught to use.
1.[(-4)+{-2}]*(-5)^2-9; divide 8 by -4 (it is the innermost parentheses problem)
2. [(-6)]*-5^2-9; next innermost parentheses problem
3. [(-6)]*25-9; exponents
4. -150-9; multiplication
5. -159; subtraction/addition depending on how you want to look at it