甲 = 35%÷(1-15%) = 35/85 = 7/17 ≈ 41.18%乙 = 29%÷(1-15%) = 29/85 ≈ 34.12%丙 = 21%÷(1-15%) = 21/85 = 3/17 ≈ 17.65%
