已知二分之A=三分之B等于四分之C,
A=C/2
B=3C/4
A+B+C分之3A-2B+5C的值
=(3A-2B+5C)/(A+B+C)
=(3*C/2-2*3C/4+5C)/(C/2+3C/4+C)
=5C/(9C/4)
=20/9