In the anion of borax, [B4O5(OH)4]^2-, the number of B-O-B bridges and the number of sp^3 hybridised boron atoms are, respectively,

The anion has a bicyclic structure of two fused six-membered rings sharing a bridging oxygen. Of the nine oxygens, $5$ are bridging (each bonded to two B) and $4$ are in terminal $\mathrm{OH}$ groups, giving $5$ B-O-B links. Two boron atoms are three-coordinate (trigonal planar, $sp^2$, each carrying one OH), and two are four-coordinate (tetrahedral, $sp^3$, each carrying one OH and bearing the negative charge). So the answer is $5$ and $2$.