6-7/15-4/9
=6-(7/15+4/9)
=6-(21/45+20/45)
=6-41/45
=5又4/45
原式=6-(7/15+4/9)
=6-41/45
=5+45/45-41/45
=5+4/45
=229/45
原式
=6-(7/15+4/9)
=6-(21/45+20/45)
=6一41/45
=5又4/45
解:简便运算如下:
6-7/15-4/9
=6-[(7x3)/(15x3)+(4x5)/(9x5)]
=6-[21/45+20/45]=6-41/45
=5又45/45-41/45
=5又4/45