Question

If a vendor charges p dollars each for
rugby shirts, then he expects to sell 2000 _ 100p shirts at
a tournament.

Answer 1

Question:
I am not sure what you are trying to ask but this sounds like algebra. And this questions seems incomplete. Please post any questions that are part of it.

p = unit price in dollar of a rugby shirt
2000-100p = number of unit that he expect to sell
R(p) = Total revenue

so my guess would be
(^ means place as exponent)

R(p) = p(2000-100p)
R(p) = 2000p - 100p^2


so example on how to use it
-let say the vendor charges 5 dollars each

R(5) = (2000x5)-((100)(5x5))
R(5) = 10000-2500
R(5) = 7500