linear functions-fill the tank

Question

an oil tanker can only hold 1785000.it takes hose a takes 20 hours to fill up the tank and 30 hours with hose b.what is the constant rate of change for both hoses?use these rates to write an equation with any given number of hours.

Answer 1

1785000 barrels?/20 hr = 89250 b/hr

1785000 barrels?/30 hr = 59500 b/hr

89250 b/hr(x hr) + 59500 b/hr(x hr) = 1785000

148750 x = 1785000

x = 12 hr.