Rectangle A: breadth = 7 cm, length = a cm (whole number).
Rectangle B: breadth = 8 cm, length = b cm (whole number, b > a).
Total area = 200 cm².

• 7a + 8b = 200.
• Rearranging: 7a = 200 − 8b.
• Try whole-number values of b such that (200 − 8b) is positive and divisible by 7:
• b = 4: 200 − 32 = 168, a = 168 ÷ 7 = 24. But 24 > 4 (reject, a must be less than b).
• b = 11: 200 − 88 = 112, a = 112 ÷ 7 = 16. But 16 > 11 (reject).
• b = 18: 200 − 144 = 56, a = 56 ÷ 7 = 8. 8 < 18. ✓
• So a = 8, b = 18.
• Difference in lengths = 18 − 8 = 10 cm.

Final Answer: 10 cm