Every chance-experiment question is the same three moves: list the sample space, count the favourable outcomes, then divide.
The Three Moves
One — list the sample space. That's just every outcome that could happen, written out. For a die it's 1, 2, 3, 4, 5, 6. For two coins it's HH, HT, TH, TT. Each one must be equally likely (more on that next rung).
Two — count the favourable ones. Read the question and tick the outcomes that count as a win. "An even number" on a die ticks 2, 4 and 6 — three of them.
Three — divide. P(event) = favourable ÷ total. Three evens over six faces: 3/6, which tidies to 1/2.
A Worked One
Flip two coins; what's the chance of exactly one head? Sample space: HH, HT, TH, TT — four outcomes. Favourable: HT and TH — two of them. So P = 2/4 = 1/2. Notice we listed all four before counting, so nothing got missed.
Fractions, Decimals or Percentages
The answer is a fraction first, but you can dress it any way: 1/2 = 0.5 = 50%. Same chance, three outfits. Pick whatever the question seems to want.