几道简算题.

题目

几道简算题.
[(9/10-17/72+2.6/26)/(25/27-1/9)]/18.75
（3-1又8分之1+1又7分之1）×1又13分之8-3又56分之一
1-5/6+7/12-9/
20+11/30-13/42+15/56-17/72
第三行和第四行是一道题目,不要看错了.
第一第二题好像不能简算.

答案

[(9/10-17/72+2.6/26)/(25/27-1/9)]/18.75
=[(9/10-17/72+1/10)/(25/27-3/27)]/18.75
=[(1-17/72)/(22/27)]/18.75
=[(55/72)/(22/27)]/18.75
=[(5/8)/(2/3)]/18.75
=(15/16)/(300/16)
=15/300
=1/20
=0.05
（3-1又8分之1+1又7分之1）×1又13分之8-3又56分之一
=(3-9/8+8/7)*(21/13)-169/56
=[(168-63+64)/56]*(21/13)-169/56
=(169/56)*(21/13-1)
=(169/56)*(8/13)
=13/7
1-5/6+7/12-9/20+11/30-13/42+15/56-17/72
=1-10/12+7/12-9/20+11/30-13/42+15/56-17/72
=1-3/12-9/20+11/30-13/42+15/56-17/72
=1-5/20-9/20+11/30-13/42+15/56-17/72
=1-1/5+11/30-13/42+15/56-17/72
=1-6/30+11/30-13/42+15/56-17/72
=1+1/6-13/42+15/56-17/72
=1+7/42-13/42+15/56-17/72
=1-1/7+15/56-17/72
=1-8/56+15/56-17/72
=1+1/8-17/72
=1+9/72-17/72
=1-1/9
=8/9