①2.3+5.5-2.3+5.5
②3.6×5.5÷3.6×5.5
③6.8÷3.4×6.8÷3.4
④5.5-2.3+5.5-2.3
⑤3.6×5.5÷(3.6×5.5)
⑥6.8÷3.4×(6.8÷3.4)