What is -13 minus a positive 13 and 89 minus a positive 107?

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

What is the result of adding the system of equations? 2x+y=4 3x-y=6

Can someone tell me if this is perpendicular? !