Hello there,
So you have two fractions 2/5 and 1/4, but none of them have the same denominator... However a LCD that you can get from both of these is 20, so if you multiplied 4 on the top and the bottom for 2/5, you would get 8/20, and for 1/4, multiply 5 on the top and the bottom, and soon you end up with 5/20. If you added these two fractions together, now knowing that they have the same denominator... you would end up with 13/20 which is the answer to your problem.
Hope this was helpful for you :)