Answer:
A - 3
B - 6
Explanation:
The valency of hydrogen atom is +1
The valancy of an atom of other element combining with the hydrogen atom can be determined from the number of associated hydrogen.
when H combines with A, three atoms of hydrogen are used. Thus the valency of element A is -3
Now B combines with two molecules of A whose valency is -3
The valency of B would be twice the valency of element A i.e 6
if hydrogen combines with B, then the compound formed will be BH6
