Find the unit rate in feet per second
300 yards over 1 minute

In order to find the unit rate in ft / sec of 300 yards / min. We first have to elicit the conversion values for each unit of measurement, this will allows us identify how much will we multiply in order to get the goaled value.
Conversion values:
1.    1 yard = 3 feet
2.    1 minute = 60 seconds

Solution:
1.    300 yards x 3 feet/1 yard = 900 feet
2.    1 minute x 60 seconds / 1 minute = 60 seconds

Thus, 900ft/60sec