My teacher showed me this riddle can anyone help???

Ihave trouble finding the nth term of a linear sequence

What numbers are included in the set of integers? what numbers are not included?

The revenue each season from tickets at the theme park is represented by t(c)=5x. the cost to pay the employees each season is represented by r(x)=(1.5)^x. examine the graph of the combined function for total profit and estimate the profit after four seasons