Step-by-step explanation:

Let's solve the problem step by step:

1. The weed trimmer was purchased for P40 and was marked up 60% on cost, so the selling price during the July 4 sale was:

P40 + 60% of P40 = P40 + P24 = P64

2. During the sale, it was marked down 25%, so the sale price becomes:

P64 - 25% of P64 = P64 - P16 = P48

3. On September 1, it was marked up 30% from the sale price, so the price became:

P48 + 30% of P48 = P48 + P14.40 = P62.40

4. Finally, it was marked down 20%, so the final selling price becomes:

P62.40 - 20% of P62.40 = P62.40 - P12.48 = P49.92

Therefore, the final selling price of the weed trimmer is P49.92.