填运算符号 (1 1 1 + 1 × 1 + 1 = 1 ) 2 × 2 2 2 2 1 1 (2) 2 - 2 1 1 1 + 2 ÷ 2 ÷ 2 = 2 1 1 1 1 1 (3) 2 + 2 + 2 ÷ 2 ÷ 2 = 3