Answer: He is 3.8 miles away from his house.
Explanation :
Distance the first trail took him away = (+) 4.5 miles
( We will show it with positive sign as it increase the distance away from the house)
Distance the second trail took him closer = (-) 2.4 miles
(We will show it with negative sign as it decreases the distance)
Distance the third trail took him far away = (+) 1.7 miles
Now , total distance = 4.5-2.4+1.7
= 3.8 miles
∴ He is 3.8 miles far his house.