题目内容：

[12+21*45*10.2]除以[15*4*0.7*51]

优质解答

（12+21*45*10.2）/(15*4*0.7*51)
=12/(15*4*0.7*51)+(21*45*10.2)/(15*4*0.7*51)
=(3/15)*(4/4)*(1/0.7*51)+(21/0.7*2)*(45/115)*(10.2/51*2)
=1/(5*0.7*51)+15*3*0.1
=2/357+4.5
=4又361/714