Let A be the pound Andre picked, J be the pounds Jamie picked and M be the pound Marie picked. Since Andre picked three times as many pounds as Maria, we have
[tex]\begin{gathered} A=3M \\ \text{which gives} \\ M=\frac{A}{3}\ldots(1) \end{gathered}[/tex]Similarly, since Jane picked 2 times as many pounds as Andre, we have
[tex]J=2A\ldots(2)[/tex]and since the total weight is 840 pounds, we get
[tex]A+J+M=840\ldots(3)[/tex]By substituting equation (1) and (2) into equation (3), we have
[tex]A+2A+\frac{A}{3}=840[/tex]which gives