I would try drawing the line on a coordinate plane to help.
Answer:

Step-by-step explanation:
A road is perpendicular to a highway leading to a farmhouse d miles away.
An automobile passes through the point of intersection with a constant speed
= r mph
Let x be the distance of automobile from the point of intersection and distance between the automobile and farmhouse is 'h' miles.
Then by Pythagoras theorem,
h² = d² + x²
By taking derivative on both the sides of the equation,




When automobile is 30 miles past the intersection,
For x = 30

Since 
Therefore,


The domain of the graph is all real numbers because the value doesn’t have an end point.
Sin 45 = X / 14
X = 14 * sin45
X = 7√2≈9.89949
Thus ladder will reach to ≈ 9.9 (rouded-up) foot height in the building