答：六年级数学脱式计算如下：
1/4X8Ⅹ5/6
=2X5/6
=5/3
0.75Ⅹ99十0.75
=0.75X（99十1）
=0.75X100
=75
4/7X5十4/7Ⅹ2
=4/7X（5十2）
=4/7Ⅹ7
=4
5/8X2/5÷4/3
=5/8X2/5×3/4
=1/4X3/4
=3/16
97Ⅹ1/98
=（98一1）x1/98
=98X1/98一1/98
=1一1/98
=97/98。…
根据题意分析:脱式计算的过程及结果如下所示:
520÷(48＋4)×81–729–71
＝520÷52×81–729–71
＝10×81–729–71
＝810–729–71
＝810–(729＋71)
＝810–800
＝10
