f(x) = -20x + 2560....x represents number of minutes
domain is ur x value(ur minutes) and the range is ur f(x) value (or y value)...which is the total amount of water left in the tank
x f(x) = -20x + 2560 y
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10 f(10) = -20(10) + 2560 2360
20 f(20) = -20(20) + 2560 2160
30 f(30) = -20(30) + 2560 1960
60 (1 hr) f(60) = -20(60) + 2560 1360
let me break it down for you..
at 10 minutes, there will be 2360 oz of water in the tank
at 20 minutes, there will be 2160 oz of water in the tank
at 30 minutes, there will be 1960 oz of water in the tank
at 60 minutes (or 1 hr), there will be 1360 oz of water in the tank