Answer:
option 3
Step-by-step explanation:
![(4 + 3) \sqrt[5]{x {}^{2}y } = 7 \sqrt[5]{ {x}^{2}y }](https://tex.z-dn.net/?f=%284%20%2B%203%29%20%5Csqrt%5B5%5D%7Bx%20%7B%7D%5E%7B2%7Dy%20%7D%20%3D%207%20%20%5Csqrt%5B5%5D%7B%20%7Bx%7D%5E%7B2%7Dy%20%7D%20)
This is esay to do when you realize the the speed of mowing is addtive. This is if John mows at 1 lawn / (2/3) hour and Gerge mows at 1 lawn / 1hour, the total speed of mowing is:
1 / (2/3) + 1 = 3/2 + 1 = 5/2
=> 5/2 of lawn per hour
Now, the time is calcualted as the amount of lawn divided by the speed:
1 lawn / (5/2 lawn/hour) = 2/5 hour.
Answer: 2/5 of an hour.
The base is 5 because when you divide 31.5 by 6.3 it's 5
