2\begin{gathered}x=primul\ raft\\ \frac{x}{4}=al\ doilea\ raft\\ \frac{1}{3}(x+\frac{x}{4})=al\ treilea\ raft\\ x+\frac{x}{4}+\frac{1}{3}(x+\frac{x}{4})=80\\ \frac{5x}{4}+\frac{x}{3}+\frac{x}{12}=80\\ 15x+4x+x=960\\ 20x=960=\ \textgreater \ x=48\ carti\ pe\ primul\ raft\\ \frac{48}{4}=12\ carti\ pe\ al\ doilea\ raft\\ \frac{1}[3}(48+12)=\frac{1}{3}*60=20\ carti\ pe\ al\ doilea\ raft.\end{gathered}
(nu este rsp meu)