13又4/19+86又15/19×0.25+0.625×86又15/19+86又15/19×0.125
=13又4/19+86又15/19[0.25+0.625+0.125]
=13又4/19+86又15/19×1
=[13+86]+[4/19+15/19]
=99+1
=100