Step 1: Understanding the Concept:
\(\alpha\) decay: mass number decreases by 4, atomic number by 2. \(\beta\) decay: mass number unchanged, atomic number increases by 1.
Step 2: Detailed Explanation:
Start: \({}^{228}_{88}X\)
After 3\(\alpha\) decays: Mass = 228 - 3×4 = 216, Atomic = 88 - 3×2 = 82.
After 1\(\beta\) decay: Mass = 216 (unchanged), Atomic = 82 + 1 = 83.
Element with Z=83 is Bi. So Y = \({}^{216}_{83}\mathrm{Bi}\).
Step 3: Final Answer:
\({}^{216}_{83}\mathrm{Bi}\)