Agricola filiabus pecuniam dat.

Does this mean 'the farmer gives money to his daughters'?
If so, why 'filiabus ' isn't change its form?

Question

Agricola filiabus pecuniam dat.

Does this mean 'the farmer gives money to his daughters'? 
If so, why 'filiabus ' isn't change its form?

Answer

It is " to the  daughters " and it takes the ending abus to differ from the dative masculine "filiis" which is the same. 
The same ending is used for dea, ae, to the goddesses, and it differs from deis to the gods.

Answer

It depends on context. If the sentence is after agricola filias amici eius salutat, then it is not talking about his daughters.