How to write a piecewise-defined function word problem?

Question

I want to know how to write a piecewise-defined function word problem that applies to the real-world.

Answer 1

one example would be:

the restaurant might have an offer

1 - 50 people's plate - cost $20 / plate

51 - 100 people's plate - cost $18 / plate

101 - 150 people's plate cost $16/ plate

151 - 200 people's plate - cost $14/ plate and so on.

where the number of people would be x-axis and cost would be y-axis

The more you buy the more discount you get.