a/2等于b/3等于c/4等于200820072006,令200820072006=m,则
a = 2m,b = 3m,c = 4m
所以3a+b-2c =6m+3m-8m= m
c-b+a =4m-3m+2m= 3m
3a+b-2c/c-b+a=3m/m=3