Answer:
The maximum revenue is 32. 
p=9 gives the store the maximum revenue 
Explanation:
Hi, since the term with the variable p is negative (-2p) the maximum revenue is given by the lower price (p). 
So, substituting with the lowest price p=9 in the expression: 
-2p + 50 
-2(9) +50 
-18+50 
32 
The maximum revenue is 32. 
p=9 gives the store the maximum revenue 
Feel free to ask for more if needed or if you did not understand something.