Answer:
1.2 hours
Step-by-step explanation:
A fills 1/2 tank per hour; B fills 1/3 tank per hour, so together they fill ...
1/2 +1/3 = 3/6 +2/6 = 5/6 . . . . tank per hour
The reciprocal of this rate give the rate in the units we want:
6/5 hours per tank.
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At that rate, it will take 6/5 = 1.2 hours to fill the tank.
