30÷ [(1/4+2/7)×7/20]
=30÷ (1/4×7/20+2/7×7/20)
=30÷ (7/80+1/10)
=30÷3/16
=160
(2/3-2/5)÷(1/8+5/12)
=[(2/3-2/5)×120]÷[(1/8+5/12)×120]
=(2/3×120-2/5×120)÷(1/8×120+5/12×120)
=(80-48)÷(15+50)
=32/65
( 2.8 + 3.85 ÷ 3.5 ) × 4.6
=(2.8+1.1)× 4.6
=3.9× 4.6
=4× 4.6-0.1× 4.6
=18.4-0.46
=17.94
=30÷ (1/4×7/20+2/7×7/20)
=30÷ (7/80+1/10)
=30÷3/16
=160
(2/3-2/5)÷(1/8+5/12)
=[(2/3-2/5)×120]÷[(1/8+5/12)×120]
=(2/3×120-2/5×120)÷(1/8×120+5/12×120)
=(80-48)÷(15+50)
=32/65
( 2.8 + 3.85 ÷ 3.5 ) × 4.6
=(2.8+1.1)× 4.6
=3.9× 4.6
=4× 4.6-0.1× 4.6
=18.4-0.46
=17.94
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第1个回答 2012-07-08
先算括号里面的除法 再算括号里的加法 得出的结果 再算括号外的乘法
第2个回答 2012-07-08
30÷[(1/4+2/7)×7/20]
=30÷(1/4×7/20+2/7×7/20)
=30÷(7/80+1/10)
=30÷(7/80+8/80)
=30÷3/16
=30×16/3
=160
(2/3-2/5)÷(1/8+5/12)
=(10/15-6/15)÷(3/24+10/24)
=4/15÷13/24
=4/15×24/13
=32/65
(2.8+3.85÷3.5)×4.6
=(2.8+1.1)×4.6
=3.9×4.6
=(4-0.1)×4.6
=4×4.6-0.1×4.6
=18.4-0.46
=17.94
=30÷(1/4×7/20+2/7×7/20)
=30÷(7/80+1/10)
=30÷(7/80+8/80)
=30÷3/16
=30×16/3
=160
(2/3-2/5)÷(1/8+5/12)
=(10/15-6/15)÷(3/24+10/24)
=4/15÷13/24
=4/15×24/13
=32/65
(2.8+3.85÷3.5)×4.6
=(2.8+1.1)×4.6
=3.9×4.6
=(4-0.1)×4.6
=4×4.6-0.1×4.6
=18.4-0.46
=17.94
第3个回答 2012-07-08
30/[(1/4+2/7)*7/20]
=30/[1/4*7/20+2/7*7/20]
=30/[7/80+1/10]
=30/[7/80+8/80]
=30*16/3
=160
(2/3-2/5)/(1/8+5/12)
=4/15*24/13
=96/195
( 2.8 + 3.85 ÷ 3.5 ) × 4.6
=17.94
=30/[1/4*7/20+2/7*7/20]
=30/[7/80+1/10]
=30/[7/80+8/80]
=30*16/3
=160
(2/3-2/5)/(1/8+5/12)
=4/15*24/13
=96/195
( 2.8 + 3.85 ÷ 3.5 ) × 4.6
=17.94
第4个回答 2012-07-08
=(2.8+1.1)*4.6=3.9*4.6=17.94哥笔算的哦！求采纳！