Question

David is rowing a boat upstream. The river is flowing at a speed of 2 miles per hour. David starts rowing at a speed of 6 miles per hour, and his speed decreases at a rate of 1.5 miles per hour.
The equation gives the speed of the boat after David has rowed for x hours? can someone help
y=4+1.5x
y=4-1.5x
y=6-1.5x

Answer 1

Hello there.

David is rowing a boat upstream. The river is flowing at a speed of 2 miles per hour. David starts rowing at a speed of 6 miles per hour, and his speed decreases at a rate of 1.5 miles per hour.
The equation gives the speed of the boat after David has rowed for x hours? can someone help

y=4-1.5x

Answer 2

The equation that gives the speed of the boat after David has rowed for x hours is y=4-1.5x. 

The direction David is rowing (upstream) is the positive direction. That makes the direction the river is flowing negative. David rows at 6 mph, but the river is flowing at 2 mph in the opposite direction. That means his "net" speed, relative to an observer on the ground, is 6-2 = 4 mph. He loses 1.5 mph of his speed every hour, so after x hours, his speed is 4-1.5x.