[hsebast1]

AlF3 is soluble in liquid HF, but dissolves if NaF is present. When BF3 is added tot he solution,AlF3 precipitates.
 Can u plz explain y. i do have a sense of wat is goin on...

[csrscience.com]

What you are saying doesn't make much sense.. It is soluble in HF but dissolves if NaF is present?
... it seems like they are almost contradicting each other the way you worded it...

My guess for what it is you are asking is that the reason why AlF3 is more soluble in NaF than in HF is because the Na+ and the F- fully dissociate, while HF is a weak acid and does not?
or vice versa.. not sure haha

[AWK]

Soluble H₃AlF₆ and Na₃AlF₆ are formed.
BF₃ decomposes this complex compoumd forming stronger complex HBF₄ or NaBF₄, hence AlF₃ precipitates.