Let's analyze the given diagrams step by step.

(a) Diagram:

1. Relationships provided:

   • $A + 200 = 3000$
   • $A + 500 = 7500$
   • $B \div 100 = 6000$
   • $B \div 400 = 3000$

2. Finding $A$:

   • From $A + 200 = 3000$,
     $A = 3000 - 200 = 2800$.
   • From $A + 500 = 7500$,
     $A = 7500 - 500 = 7000$.

   Conclusion: $A$ seems to be 2800, as it satisfies the first condition.

3. Finding $B$:

   • From $B \div 100 = 6000$,
     $B = 6000 \times 100 = 600000$.
   • From $B \div 400 = 3000$,
     $B = 3000 \times 400 = 1200000$.

   Conclusion: There's a conflict. Check whether the pattern suggests two different values.

(b) Diagram:

1. Relationships provided:

   • $C \div 200 = 26200$
   • $C \div 300 = 39300$
   • $D \div 200 = 13100$

2. Finding $C$:

   • From $C \div 200 = 26200$,
     $C = 26200 \times 200 = 5240000$.
   • From $C \div 300 = 39300$,
     $C = 39300 \times 300 = 11790000$.

3. Finding $D$:

   • From $D \div 200 = 13100$,
     $D = 13100 \times 200 = 2620000$.

Let me know if you need clarifications!