a) \(y+30\%y=-1.3\)
\(y+\dfrac{3}{10}y=\dfrac{-13}{10}\)
\(y\left(1+\dfrac{3}{10}\right)=\dfrac{-13}{10}\)
\(y\left(\dfrac{10}{10}+\dfrac{3}{10}\right)=\dfrac{-13}{10}\)
\(y\cdot\dfrac{13}{10}=\dfrac{-13}{10}\)
\(y=\dfrac{-13}{10}:\dfrac{13}{10}\)
\(y=\dfrac{-13}{10}\cdot\dfrac{10}{13}\)
\(y=-1\)
Vậy \(y=-1\).
b) \(y-25\%y=\dfrac{1}{2}\)
\(y-\dfrac{1}{4}y=\dfrac{1}{2}\)
\(y\left(1-\dfrac{1}{4}\right)=\dfrac{1}{2}\)
\(y\left(\dfrac{4}{4}-\dfrac{1}{4}\right)=\dfrac{1}{2}\)
\(y\cdot\dfrac{3}{4}=\dfrac{1}{2}\)
\(y=\dfrac{1}{2}:\dfrac{3}{4}\)
\(y=\dfrac{1}{2}\cdot\dfrac{4}{3}\)
\(y=\dfrac{2}{3}\)
Vậy \(y=\dfrac{2}{3}\).
c) \(3\dfrac{1}{3}y+16\dfrac{3}{4}=-13.25\)
\(\dfrac{10}{3}y+\dfrac{67}{4}=\dfrac{-53}{4}\)
\(\dfrac{10}{3}y=\dfrac{-53}{4}-\dfrac{67}{4}\)
\(\dfrac{10}{3}y=-30\)
\(y=-30:\dfrac{10}{3}\)
\(y=-30\cdot\dfrac{3}{10}\)
\(y=-9\)
Vậy \(y=-9\).
