Answer:
0.2579 m³
Step-by-step explanation:
The given unit, firkin has a relation with the gallons as:
1 firkin = 9 gallons
The relation bewteen gallons and m³ is shown below as:

So,

To find how many m³ in 7.57 firkins.
So,

So, 7.57 firkins = 0.2579 m³