Solution:
Borazine has a formula B3N3H6 and has six reactive hydrogen ions. When it gets disubstituted with X, then it forms B3N3H4X2 and is called disubstituted borazine. This has four reactive hydrogen ions, therefore there are four ways through which 2X can arrange in B3N3H4X2. Therefore, the number of isomers in B3N3H4X2 is 4.