According to the meaning: 5x+3y = 335003x+7y = 43500,
Solution: x = 4000 y = 4500.
A: Roses earn 4,000 yuan per mu, while Daphne odora in Phnom Penh earns 4,500 yuan on average.
(2) If m mu of roses are planted, the planting area of Daphne odora in Phnom Penh is (30-m) mu.
According to the meaning of the question: m > 30,
Solution: m > 15,
When 15 < m ≤ 20, the total income w = 4000m+4500 (30m)+15×100+(m-15 )× 200 ≥120.
Solution: 15 < m ≤ 20,
When m > 20, the total income w = 4000m+4500 (30-m)+15×100+5× 200+(m-20 )× 300 ≥127500,
Solution: m≤20, (irrelevant),
To sum up, the planting scheme is as follows:
Planting type Planting area (mu) Plan 1 Plan 2 Plan 3 Plan 4 Plan 5 Rose1617181920 Potamogeton crispus1412165438.