Here's the task out of the exam last year:

As a pricing manager at X you have estimated the following price demand function for TV 2.0 (for a price per month in USD):

x(p) = 2'000'000 - 40'000 p

--> What is the price elasticity at a price of 20 CHF? What would you recommend to do?

I know now how to solve normal elasticity tasks where P∆ is noted, but its not visible for me here - can someone help me out?

Thanks a quadrillion times :)