After a 20% tip, you pay a waitress $72. What was the original bill?

If you want to find out how to calculate a tip, you need to decide how much you appreciate the service. There is an unwritten rule that a tip should be between 10% and 20% of the total value of the bill.

$ 86.4

Step-by-step explanation:

hope this helps

so sorry if this is wrong

f(x) has value 150 at x= 0

and 0 at x= 3

so d(f(x))/dt = slope = -150/3 = -50