用简便方法计算 3⼀4-(5⼀9-1⼀4)+7⼀9

3/4-5/9+1/4+7/9=3/4+1/4+7/9-5/9=1+2/9=1又2/9
12.5%*1/3*72＝0.125*8*（9*1/3）＝1*3＝3
7/12除以【（三分之五+四分之一）*三分之二】=7/12除以【23/12*三分之二】=7/12除以23/12除以
三分之二=7/12 * 12/23 *2/3=21/46

3/4-(5/9-1/4)+7/9
=27/36-(20/36-9/36)+28/36
=27/36-9/36+20/36+28/36
=18/36+20/36+28/36
=1+28/36
=28/36

解1：
3/4-(5/9-1/4)+7/9
=3/4-5/9+1/4+7/9
=3/4+1/4-5/9+7/9
=1+2/9
=11/9

解2：
12.5%×(1/3)×72
=(125/1000)×[(1/3)×72]
=0.125×24
=0.125×8×3
=1×3
=3

解3：
(7/12)÷[(4/3+1/4)×(2/3)]
=(7/12)÷[(4/3)×(2/3)+(1/4)×(2/3)]
=(7/12)÷(8/9+1/6)
=(7/12)÷(16/18+3/18)
=(7/12)÷(19/18)
=(7/12)×(18/19)
=(7/2)×(3/19)
=21/38