Answer:
3 feet
Explanation:
Do you know how to convert yards to feet?
You first have to know how many feet are in a yard.
That's 3. 3 feet per yard.
The pipe is 6 yards long, so how many feet is that?
6 yards x 3 ft/yard = 18 feet
(Notice how yards cancelled out.)
So how many feet would you have to cut off to leave 15 feet? You can probably see that it's 3 feet, but as an equation it would be the difference between 18 and 15:
18 feet - 15 feet = 3 feet, which is how many feet need to be cut off