Recall your d = rt, distance = rate * time
let's say the boat's rate is "b" in still water, and the current's rate is "c"
as the boat goes upstream, is not really going "b" fast, the water is not still anyway, is going much slower, is going " b - c ", because the current's rate is eroding speed because is going against the current.
as the boat goes downstream, is not going "b" fast either, is going faster, is going " b + c " fast, because is going downstream and thus with the current and the current is adding speed to it. notice, it takes longer going up, 5hrs, then coming down, 3hrs, same 150 on each way.

solve for "r"
what's the boat's rate? well, 30+r = b
Answer:
2.75
Step-by-step explanation:
21.50 - 18.75 = $2.75
CAN I HAVe BRAINLIEST
Hey there!
The correct answer is 30 miles per gallon.
If he can drive 270 miles on 9 gallons, we want to find the unit rate, or miles per gallon. We can do this by dividing 270 by 9. To make it easier, we will take off the zero, and do 27/9, which is 3. Now we add the 0 back on, which gives us 30. Therefore, his average mileage is 30 miles per gallon.
Have a terrificly amazing day! :D