if 6/7 yard of material is needed to make a blanket, how many blankets can be made from 18 yards of material?

Let's work with an equation of rates (ratios):

6/7 yd material        18 yds
-------------------- = -------------------
1 blanket                        x

Then (6/7)x = 18, and   x = (7/6)(18) = 21.

21 blankets can be made from 18 yds of material.