（9又1/2+7又1/6+5又1/12+3又1/20+1又1/30）*12
=（9+7+5+3+1+1/2+1/6+1/12+1/20+1/30）x12
=(25+1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6)x12
=(25+1/2-1/6)x12
=25x12+1/2x12-1/6x12
=25x4x3+6-2
=300+4
=304计算26*27-1分之26+25*27