what type of reaction is Na2B4O7.10H2O + 2HCl -> 2NaCl(aq) + 5H2O + 4B(OH)3. (ie. double displasment, single displacement, neutralize)?

Answer 1

It's an unusual kind of double displacement.  It's easier to see if you cancel the water molecules that do not react with anything:

Na2B4O7(H2O)5 + 2 HCl → 2 NaCl + 4 B(OH)3

Answer 2

Neutralization