1. Tìm x bt: a) x-43=(57-x)-50 b) $\frac{x+2}{6}$=$\frac{-15}{6}$ 2. Tìm x ∈ Z bt: a) $\frac{1}{3}$+$\frac{3}{35}$<$\frac{x}{210}$<$\frac{4}{7}$+$\frac{3}{5}$+$\frac{1}{3}$ b) $\frac{3}{5}$+$\frac{-14}{3}$<x<$\frac{8}{5}$+$\frac{8}{10}$ c) $\frac{5}{21}$+$\frac{-3}{7}$<$\frac{x}{21}$<$\frac{-2}{7}$+$\frac{8}{21}$

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