Answer:
1 yard = 3 feet
We can re-write this by dividing both sides by yards or feet to get
1 = 3 feet / 1 yard
or
1 yard / 3 feet = 1
Since we're solving for feet we want yards to cancel, so use the top proportion
(3 feet / 1 yard)(100 yards) = 300 feet / 1 = 300 feet