If the fisherman caught 30 fish during the day and some of them weighed more than 2 kg, then we can assume that he caught two types of fish: those that weigh more than 2 kg and those that weigh less.
Let's say that the fisherman caught x fish that weigh more than 2 kg. Then, he caught 30 - x fish that weigh less than or equal to 2 kg.
The fisherman can sell each fish that weighs more than 2 kg for £5.99. Therefore, the total revenue from these fish would be:
£5.99 * x
The remaining fish, which weigh less than or equal to 2 kg, are sold to a pet food manufacturer at 75% of the price. This means that the fisherman will receive 75% of the original price for these fish, which is:
75% * £5.99 = £4.49
The total revenue from these fish would be:
£4.49 * (30 - x)
Therefore, the total revenue for the day would be:
£5.99x + £4.49(30 - x)
Simplifying this equation, we get:
£1.50x + £134.70