I assume the question means to ask for the "proportion", not the "portion" (which could be interpreted in different ways).

For Statement 1 alone, you can just imagine 2 people study all three languages, and 1 studies Spanish and French only. That gives 3 people studying Spanish, so 5 must study German and 8 must study French. But we can then freely decide how many study German and French only (we can have between 0 and 3 people in that group), and changing that value changes the answer to the question. (edited the first sentence, which had a typo; I had written "only Spanish" when I meant "Spanish and French only").

Statement 2 is sufficient alone. Notice if the ratio of Spanish to German to French is 3 to 5 to 8, then when we sum the number taking Spanish and the number taking German, we must get the number taking French. But no one only takes French. So for that sum to work, everyone taking Spanish must take French, and everyone taking German must take French, and no one can take all three languages (if it's not clear that needs to be true, you can label a Venn: if s take Spanish only, g take German only, z take Spanish and German only, x take French and Spanish only, y take French and German only, and t take all three, then s + z + x + t taking Spanish, g + z + y + t taking German, and x + y + t taking French, and since the total taking Spanish and the total taking German sum to the total taking French, s + z + x + t + g + z + y + t = x + y + t, and s + 2z + t + g = 0, and since s, z, t and g all need to be at least zero, they all must equal zero). So there are only two categories that can have a nonzero number of students: French and Spanish only, and French and German only. From the ratio we must have 3k people in French and Spanish only, and 5k in French and German only, and of the 8k people taking French, 5k take German too, and the proportion is 5/8.
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