Share of hidden total: Alpha's share

The total isn't given — sum all the parts first, then share = part ÷ that total. The correct answer is 38.0. Traps to avoid: 20.20 comes from the "wrong slice" error; 92 comes from the "forgot to divide" error; 31.50 comes from the "wrong total" error; 61.30 comes from the "divided by others" error.