Step 1 :Convert the mixed numbers to improper fractions. The initial length of the sandwich is \(5 \frac{7}{8}\) feet, which is \(\frac{47}{8}\) feet. The eaten length is \(3 \frac{3}{5}\) feet, which is \(\frac{18}{5}\) feet.
Step 2 :Subtract the two fractions to find the remaining length of the sandwich. \(\frac{47}{8} - \frac{18}{5} = \frac{111}{40}\) feet.
Step 3 :Convert the improper fraction back to a mixed number. \(\frac{111}{40} = 2 \frac{11}{40}\) feet.
Step 4 :\(\boxed{2 \frac{11}{40}}\) feet of the sandwich was left.