Explanation:
rolling the die twice as one event we get 6×6 = 36 possible outcomes.
rolling an even number on the first try gives us 3 desired outcomes (2, 4, 6).
rolling it a second time gives us again 3 desired outcomes.
in total we have
3×3 = 9 such outcomes with 2 even numbers.
the probability for that is then
9/36 = 1/4 = 0.25
FYI - we have also 9 possible outcomes for the first roll being odd and the second being even, 9 possible outcomes for the first being even and the second being odd, and 9 possible outcomes for both being odd.
together with the 9 for both being even we get the full 36 possible outcomes. no other event is possible.