(-13) +[(24 /8) x 7) - 20 =
work from the innermost brackets outwards:
(-13) + [3 x 7] - 20 =
(-13) + 21 - 20
add next:
8 - 20=
subtract
-12
Use the memory aid PEMDAS to remember which operations come first.
parentheses, exponents, multiply, divide, add, subtract, all done left to right.