1998×(-)+11×(-)-2009×(+)+3
① + + +
② × + ÷
③3.8×9.9+0.38
④(8+ )÷4
⑤6÷ + ÷6
⑥ ÷[( + )× ]
①
②
③
④
①÷×
②×3.2+6.8÷
③105×(+)
④﹣+﹣
⑤6.4÷[(3﹣1.4)×]