58/7+5.8-23/7+4.2
=(58/7-23/7)+(5.8+4.2)
=35/7+10
=5+10
=157/8*1/4+0.25*0.1257/8*1/4+0.25*0.125

=7/8*1/4+1/8*1/4

=(7/8+1/8)*1/4
=1*1/4
=1/4

请采纳，谢谢