\(a,12\dfrac{1}{3}:\left(\dfrac{-5}{8}\right)-6\dfrac{1}{3}:\left(\dfrac{-5}{8}\right)=\dfrac{37}{3}:\left(\dfrac{-5}{8}\right)-\dfrac{19}{3}:\left(\dfrac{-5}{8}\right)=\left(\dfrac{37}{3}-\dfrac{19}{3}\right):\left(\dfrac{-5}{8}\right)=6:\left(\dfrac{-5}{8}\right)=\dfrac{-48}{5}\)
\(b,7^{2x-1}=49\\ 7^{2x-1}=7^2\\ 2x-1=2\\ 2x=2+1\\ 2x=3\\ x=3:2\\ x=1,5\\ Vậyx=1,5\)