Please solve this problem?

Question

The profit on a watch is given by P = x^2– 13x – 80, where x is the number of watches sold per day. How many watches were sold on a day when there was a $50 loss?

Answer 1

15 watches.

Set the equation equal to your $50 loss:
x² - 13x - 80 = -50

Add 50 to both sides:
x² - 13x - 30 = 0


Using the quadratic formula or by factoring, you get
x = -2 or 15

Since you can't sell -2 watches, the answer has to be 15.

Answer 2

i guess its 470
i hope that's right