the solution to this problem is to make a graph, and plot the data that is given. Place the room rate on the Y axis, and the occupancy on the X axis. the formula for a straight line on a graph is y = mx + b where y = room rate, m = slope of the line, and b = the intercept on the Y axis. in this case, the slope is $-15/150 = -10
we can then compose a table of room price versus occupancy based on the data in the problem
granted, there are only two data point pairs to plot on an X-Y graph, but it can be estimated that
rental fee per room $90 $75 $72.50 $60 $45 $37.50
number of rented rooms 300 450 525 600 750 800
gross revenue $27,000 33,750 41,688 36,000 33,750 30,000
from this table, it can be seen that the minimum nightly rental will be $37.50 per room
maximum revenue will occur at a room rental of $72.50 (approximately)