1 foot = 12 inches.
0.75 feet x 12 inches per foot = 9 inches per day.
1 day = 24 hours.
9 inches / 24 hours = 0.375 inches per hour ( 3/8 inch per hour)
Not sure if you need a decimal or fraction for an answer so I provided both.
Let same number of hours = x,
since the salary earned is also the same, then
Salary of supervisor A = $25x
Salary of supervisor B = $20(30)+$30(x-30)
Equating
25x=600+30(x-30)
30x-25x=900-600
5x=300
x=60 hours
Check:
Salary of supervisor A = 25*60=1500
Salary of supervisor B = 20*30+30*(60-30)=600+900=1500, ok.
It's a little hard picturing that, do you happen to have a photo of the coordinate plane or graph?