correct answer is: c) 80 km

Explanation

Let, he travelled ‘x’ km overall.
Now, \large\frac{3}{8} of his journey he travelled by train.
\therefore The man travelled by train \left(x\times\large\frac{3}{8}\right) km.
\rightarrow \large\frac{3x}{8} km.
Now, \large\frac{2}{5} of journey he travelled by bus.
\therefore The man travelled by bus \left(x\times\large\frac{2}{5}\right) km.
\rightarrow \large\frac{2x}{5} km.
And now, 18 km he travelled by foot.
So that, The man total travelled =\left(\frac{3x}{8}+\frac{2x}{5}+18\right) km.
\rightarrow \large\left(\frac{15x+16x+720}{40}\right) km.
\rightarrow \large\left(\frac{31x+720}{40}\right) km.
According to the question,
x=\large\left(\frac{31x+720}{40}\right) km
\rightarrow 40x=31x+720 km _{[cross multiply]}
\rightarrow \left(40x-31x\right)=720 km _{[interchange]}
\rightarrow 9x=720 km
\rightarrow x=\large\frac{720}{9} km
\rightarrow x=80 km
\therefore The man travelled overall 80 km.
Ans: Overall the man travelled 80 km.

Another form of this specific math question exists:

1. A man traveled fractions of his journey by train and bus, and walked the rest, totaling 18 km. How far did he travel in total?
2. Find out the entire journey distance when a man covered 3/8 by train, 2/5 by bus, and the rest by foot with the remaining distance given as 18 km.
3. Calculate the total distance traveled by a man who completed 3/8 of his journey by train, 2/5 by bus, and the remaining 18 km on foot.