Explanation:
A)
We know that the water level is decreasing by 25 ft per day. This means that -25x would be the first part of the equation.
We also know that the water level starts at 45 ft when x=0.
Given this information, we can create an equation as follows

B)
Now that we have our equation, we can plug in 10 for x in order to find the height of the river

This means that after 10 days, the height of the river is -205 ft.