17 3 5 - 11 1 2 is ambiguous. I believe you meant 17 3/5 - 11 1/2. Must supply that " / " to indicate division.
It might be easier if you write this problem vertically: Compute the following:
17 3/5
-11 1/2
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Before you can do anything else, you must change the fractions 3/5 and 1/2 so that they share the same denominator (which we call the Lowest Common Denominator). Hint: The LCD here is 10.
Can you now perform this subtraction?