We have types A and B.
• One bag has 3 kg of A.
,• Seven bags have 63 kg.
[tex]\begin{gathered} 7b=63 \\ b=\frac{63}{7}=9 \end{gathered}[/tex]There are 9 kilograms in each bag. So,
[tex]A+B=9[/tex]This represents the mixture in one bag.
[tex]\begin{gathered} 3+B=9 \\ B=9-3=6 \end{gathered}[/tex]