Tính giá trị biểu thức:
\(A=\frac{15}{34}+\frac{7}{21}+\frac{9}{34}-1\frac{15}{17}+\frac{2}{3}\) \(B=16\frac{2}{7}:\left(\frac{-3}{5}\right)-28\frac{2}{7}:\left(\frac{-3}{5}\right)\)
\(C=25.\left(\frac{-1}{3}\right)^3+\frac{1}{5}-2.\left(\frac{-1}{2}\right)^2-\frac{1}{2}\)