EXPLANATION
If one piece was 8 3/8 yards long, another 6 4/5 and the another 15 3/4 we need to compute the total length as shown as follows:
The total length was:
[tex]\text{Total length=8}\frac{3}{8}+6\frac{4}{5}+15\frac{3}{4}=30\frac{37}{40}=\frac{1237}{40}=30.92\text{ yards long}[/tex]