51又2/3×3/5＋71又3/4×4/7＋91又4/5×5/9

51又2/3×3/5＋71又3/4×4/7＋91又4/5×5/9
51又2/3×3/5＋71又3/4×4/7＋91又4/5×5/9

51又2/3×3/5＋71又3/4×4/7＋91又4/5×5/9
51又2/3×3/5＋71又3/4×4/7＋91又4/5×5/9
=155/3×3/5+287/4×4/7+459/5×5/9
=155/5+287/7+459/9
=31+41+51
=123