This might help explain how to do a very similar problem.... http://www.mathopenref.com/constbisectline.html
The slant height of the pyramid is 756 feet
Change 30 hours into minutes, then divide by 20 and 25
Fabric needs to make a dress = 3 1/4
fabric needs to make jacket= 3 1/4 - 5/6
= 29/12 or 2 5/12
Hence total fabric needed for both pieces is
= 3 1/4 + 2 5/12
= 68/12 or 5 8/12 or 5 2/3 yards
