Explanation:
7.)
13 - 24 / (8 - 2) × 1³
brackets first
13 - 24 / (6) × 1³
exponents next
13 - 24 / 6 × 1
dot operations (division, multiplications) next
13 - 24 / 6 × 1 = 13 - 24×1/6 = 13 - 24/6 = 13 - 4
dash operations (adding, subtracting) last
13 - 4 = 9
8.)
-81/9×4 + 8²
no brackets, so exponents first
-81/9×4 + 64
dot operations next (often best is going left to right, but the sequence actually does not matter; e.g. -81/9×4 = -81×4/9).
-81/9×4 + 64 = -9×4 + 64 = -36 + 64
dash operations last (again, sequence does not matter, if you handle all signs correctly, but in case of doubt just go left to right).
-36 + 64 = 28