Given,
A=2,3,4,B=8,9,12
And a1∈A,b2∈B
Now finding elements where a1 divides b2 we get,
(a1,b2)∈(2,8),(2,12),(3,9),(3,12),(4,8),(4,12)
Also given, a2∈A,b1∈B
Now finding elements when a2 divides b1, we get,
(a2,b1)∈(2,8),(2,12),(3,9),(3,12),(4,8),(4,12)
Hence, Number of relations =6×6=36