If the first gardener can finish the job in 6 hours, it means that every hour he completes 1/6 of the job.
By the same logic, the second gardener completes 1/7 of the job per hour.
So, if they work together, they complete

of the job per hour.
So, after 42/13 of a hour, they'll complete the job. Since one hour is made of 60 minutes, 42/13 of a hour is

So, it will take them about 194 minutes to finish the job, i.e. about 3 hours and 14 minutes.
6 x 8 = 48, the answer is 8, just divide 48 by 6.
Answer:
a) 91 1/6 gallons
b) 2502 miles
Step-by-step explanation:
You are given a number of miles and a number of gallons for the car. The ratio of these numbers is ...
(261 mi)/(14.5 gal) = 18 mi/gal
We presume this value is constant for this car. Then the questions can be answered by forming and solving a proportion:
a) 1641 miles/(gallons) = 18 mi/(1 gal)
Multiplying by gallons and dividing by 18 mi/gal, we get
1641/18 gal = (gallons) = 91 1/6 gal
It will take 91 1/6 gallons of gasoline for Mary to drive to her friend's house.
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b) Same deal, but the miles are unknown.
(miles)/(139 gal) = (18 mi)/(1 gal)
Multiplying by 139 gal gives ...
(18 mi)·139 = (miles) = 2502 mi
139 gallons of gasoline will let Mary drive 2502 miles.