The question demands that we find a fraction of a given quantity.
The 'of ' means multiplication.
So the total distance of the journey was
\(13 \: miles\)
But they walked ¼ of the whole journey. We are supposed to find
\(\frac{1}{4} \: of \: 13 \: miles\)
\(
= \frac{1}{4} \times 13 \: miles\)
\(
= \frac{13}{4} \: miles\)
\(
= 3.25\: miles\)
Hence they walked 3.25 miles.
