Answer: The required equation is,
y = 4 - x
Step-by-step explanation:
Let x be the number of hours spent after David got tired and y represents his speed after x hours,
Given,
His initial speed in still water = 6 miles per hour,
Also, the speed of stream = 2 miles per hour,
So, his initial speed in upstream = 6 - 2 = 4 miles per hour,
Now, His speed is decreasing by 1 miles per hour in every hour,
Thus, total decrement in his speed after x hours = 1x = x
Hence, his speed after x hours = Initial speed in upstream - Decrement in speed
y = 4 - x
Which is the required equation.
