It is clear from your answer to the second part that you know the A→B scale factor is the reciprocal of the B→A scale factor. Use that fact for the other two parts of the question.
A → B = 1/3; B → A = 3
A → B = 2; B → A = 1/2
A → B = 2/5; B → A = 5/2
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It is convenient to find a unit length (or the smallest length) on the smaller figure, then see how much that is multiplied by to get the larger figure.
B : A = 1 : 3
A : B = 1 : 2
B : A = 2 : 5
Once you have these ratios, you need to determine what the notation A→B is supposed to mean. Here, we presume it means B/A.
