the second answer is correct if they messed up on the question and meant to ask for the MAD of set B
I think the 3rd answer is incorrect (I got 1.09), so you might want to double-check your 3rd answer since it is asking for "times bigger", not how much bigger, which means how many times larger is the MAD of set A than that of set B and to find how many times bigger a number is than another number, you have to divide the first number by the second number.