Verified Answer :

Technically the first pair could be:
\(\frac{3}{10}\) and \(\frac{4}{10}\)
IF that isn't an answer choice,
\(\frac{6}{20}\) and \(\frac{8}{20}\)
Is correct as well
The second would be:
\(\frac{4}{12}\) and \(\frac{9}{12}\)

3/10 and 2/5 would turn into 3/10 and 4/10. You don't have to change 3/10 because that is the common denominator.

1/3 and 3/4 would turn into 4/12 and 9/12 because 3 can go into 12 four times, so you do 1 x 4 which gives you a fraction of 4/12. You do the same with 3/4 too.