It is given that the general equation is:

Here A is the number of people attending and p is the price of ticket.
Find the values of m and b by the conditions.
When A=1850, p=17 so it follows:

When A=2700, p=13 so it follows:

Subtract (ii) from (i) to get:

Substitute the value of m in (i) to get:

So the equation becomes:

Hence the linear equation is 2A=-425p+10925.