​ What is the maximum revenue she can make?

Here are the constraints

x  + y  ≤ 36

y  ≥  3x

And we seek to maximize this

2x  +  3y

Look  at the graph of the constraints :  https://www.desmos.com/calculator/ezk3fnwmsj

The max occurs at the only corner point,  (9,27)

So......the max profit  is

2(9)  + 3(27)  =

18  +  81   =

$99