Answer:
In the original party, there were 8 fishermen.
Explanation:
A party of fishermen rented a boat for $240.
Let original number of fisherman in party be x.
So, average cost per person =

New number of fisherman in the party = x-2
So, new average cost per person =

As 2 persons withdrew, the cost increased by $10 for others.
So, equation becomes:

=>

Solving this we get the quadratic equation:

Factoring out 10 common;

=>

=>

We get the roots as (x-8) and (x+6)
So, x = 8 and x = -6(neglecting negative value)
Hence, there were 8 fisherman in the original party.