Use the top-level ratio 5:6 to find how many tulips and daisies there are, then break each group down using sub-ratios.

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• Top-level ratio 5:6 means 11 units in total.
• 66 ÷ 11 = 6 per unit.
• Tulips: 5 × 6 = 30
• Daisies: 6 × 6 = 36

For the tulips (sub-ratio 2 + 3):
• 5 parts = 6 per part
• pink: 2 × 6 = 12
• yellow: 3 × 6 = 18

For the daisies (sub-ratio 5 + 1):
• 6 parts = 6 per part
• pink: 5 × 6 = 30
• yellow: 1 × 6 = 6

Total yellow: 18 + 6 = 24.

Check: 30 + 36 = 66 = total (66). ✓

Final Answer: 24