Question 1010645
My problem is as follows:
I need to write a function of the total amount of payment (P) in the number of t-shirts ordered (N).
Here is the word problem:
a wholesale store charges $20 per t-shirt for the first 50 t-shirts, then $15 per t-shirt for those t-shirts from 51 to 125 t-shirts, and then $12 for each t-shirt from the 125th t-shirt.

I would greatly appreciate any help.
Thanks in advance.
Maria
<pre>I believe you meant: "and then $12 for each t-shirt from the 126<sup>th</sup> {{{red(cross(125th))}}} t-shirt."

This is a piece-wise function, as there're different prices for different numbers of t-shirts purchased
Number of t-shirts purchased: N 
If up to 50 t-shirts are purchased, cost is: 20N
If 51 - 125 t-shirts, inclusive, are purchased, cost is: 15(N - 50) + 20(50), or 15N - 750 + 1,000, or 15N + 250
If more than 125 t-shirts are purchased, cost is: 12(N - 125) + 15(125) + 250, or 12N - 1,500 + 1,875 + 250, or 12N + 625

We therefore get:
{{{highlight_green(P(N)=system(matrix(3,3,"$"(20N), for, 0 <= N <= 50, "$"(15N + 250),  for, 50 < N <= 125, "$"(12N + 625), for, N > 125)))}}}