Có: \(\frac{50}{68}=\frac{25}{34}\)
Theo bài ra ta có: \(\frac{25+m}{34+m}=\frac{4}{5}\)
\(\Rightarrow\frac{5x\left(25+m\right)}{5x\left(34+m\right)}=\frac{4x\left(34+m\right)}{5x\left(34+m\right)}\)
\(\Rightarrow5x\left(25+m\right)=4x\left(34+m\right)\)
\(\Rightarrow125+5xm=136+4xm\)
\(\Rightarrow m=11\)
p/s: \(x\)là dấu nhân nha!