Answer: 2/3 lawns per minute
Explanation:
A hack to easily find the unit rate is to divide the first unit by the second. In this question, it says "lawns per hour", and the first unit is lawns and the second unit is hours.
Lawns per hour = lawns/hours
6/9= 2/3
2/3 lawns per hour
Checks:
2/3x9= 18/3= 6 Lawns in 9 hours