All savings accounts are interest-bearing accounts.
Conclusion (so)
Some savings accounts have tax-free interest.
Evidence
All savings accounts are interest-bearing accounts.
Some interest-bearing accounts have tax-free interest.
Evaluate
Whenever we do Parallel Flaw, the #1 thing we look for is Nec vs. Suff errors (illegal reversals / negations), and this is indeed doing an illegal reversal.
We can choose to describe the flaw conversationally or to describe the structure and pick an answer with matching structure.
The reason the conclusion is invalid is that we don't have to think that the tax-free interest-bearing accounts are savings accounts. We know there are tax-free interest-bearing accounts, but the author is assuming those accounts are savings accounts. That's how she reaches her conclusion.
Why does she assume that? Because she's getting confused by her first premise. We know that all savings accounts are interest-bearing, but she's acting like we know that all interest-bearing accounts are savings accounts (that's the illegal reversal).
So, conversationally, we could look for an answer choice where the author assumes the reverse of one of her premises.
We can otherwise take advantage of the copycat ideas and quantifiers to map out the structure of the argument.
P: All A's are B. P: Some B's are C. C: Some A's are C.
Since SOME statements are reversible, we don't care whether the SOME premise is "Some B's are C" or "Some C's are B". Ditto for the conclusion.
What matters is that the overlapping idea in the two premises is the OUTCOME of the All statement, rather than the TRIGGER.
Goal
Find an answer that performs an illegal reversal, or look for an answer that matches this structure: P: All A's are B. P: Some B's are C. C: Some A's are C.