$$(2^{-3}+4^{-2}+6^{-1}{)}^{-1}\cdot 8.5-4$$$$(-{0.5}^{-2}+{0.2}^{-2})(3^{-1}+7^{-1})$$$$7\cdot ({2.5}^{-1}+{1.5}^{-2})(5^{-1}+9^{-1}{)}^{-1}$$$$((-1\frac{1}{3}{)}^2+(4\frac{1}{2}{)}^{-1})\cdot {1.5}^{-2}\cdot (\frac{1}{3}{)}^{-2}$$