Hi

We have ,
HCF = 2
Let let us assume the required two numbers = 2p and 2q ,
where p and q are prime to each other.
Now, A/Q
2p *2q = 84
2 (p + q) = 84
p + q = 84 / 2 = 42

42 = 1*42, 42= 2*21 , 42= 3* 12, 42= 6*7
Possible pairs of numbers satisfying this condition = 4

Hence , four pairs are of required numbers.

Thankyou