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Then, looking at every anwser response... We could eliminate [81] and all evens because they are divided by 2 and below 81... So [54], [36] and [18] are out...

Finally, to make a last check, we have :
[27] = 27 * 3 = 81

[I]
Left hand side is:
a+b-ab
Right hand side is:
b+a-ba

Both sides are equal.

[II]
Left hand side is:
a+0-a*0 = a
Right hand side is:
a

Both sides are equal.

[III]
Left hand side is:
(a+b-ab)@c=a+b-ab+c-(a+b-ab)*c=a+b-ab+c-ac-bc+abc=a+b+c-ab-bc-ca+abc
Right hand side is:
a@(b+c-bc)=a+b+c-bc-a*(b+c-bc)=a+b+c-bc-ab-ac+abc=a+b+c-ab-bc-ca+abc

rdg,
for question 2 answers also need to be applied with same rule for ODD as mentioned in Question stem.
So if you pick answer A) which is 81 inside a square then value for it is actually 81*3 which is not what you calculated, right?
So answer is D which is equivalent of 27 * 3 = 81

rdg, for question 2 answers also need to be applied with same rule for ODD as mentioned in Question stem. So if you pick answer A) which is 81 inside a square then value for it is actually 81*3 which is not what you calculated, right? So answer is D which is equivalent of 27 * 3 = 81

Thanks kyatin.
I understand what you meant. It will be (D).