What is making this question challenging (to some extent, however, it is not the hardest question on the planet) is the wording of the question itself.
The same is when you are approaching a test such as GRE: it is tricky, NOT difficult.
Back to the question: always, always break it into chunks. Do not think for a moment to the goal (the question's solution) you have to reach but the way to go through. You will be there without believing you are already in your end zone.
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If A*B is the greatest common factor of A and B
This means that we do have two numbers and we do have the GCF of these. A*B is simply a representation of these numbers. We could call them X and Y or Tom and Jerry. The symbol * is impossible of being a multiplication.
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A$B is defined as the least common multiple of A and B
Is the same of above, only that here we do have the LCM
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and A∩B is defined as equal to (A*B) $ (A$B)
this actually means: the common area (the interception) between A and B. Our A is A*B and our B is A$B:
GCF $ LCM where $ is just a symbol to show the LCF.
Actually, we have to find the GCF of A*B, the LCM of A$B and then the LCM of the two combined.
A= 12 and B = 15. The GCF of 12 and 15 is 3. The LCM of 12 and 15 is 60. The LCM of both (3 and 60) is 60. E is the answer.
is it not easy to look this way ??
Ask for further assistance.
Regards