We know, 3 feet = 1 yard.
We have to convert feet to yards to calculate the ratio so that the final answer doesn't have any unit.
Therefore, 21 feet =
= 7 yards
Thus, the ratio
![(21feet)/(8yards) =(7yards)/(8yards) =(7)/(8)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/a4ksmitp1129ag6cdmek6r28l61cuhync8.png)
The fraction
is already in its simplest form.
Therefore, the given ratio as a fraction in the simplest form without any units is
![(7)/(8)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/heyfbusvelejms7vfs1jao2x26yjrbbp8v.png)