X=3a+1=5b+2=7c+3
a=(5b+1)/3=2b-(b-1)/3,
b-1=3n,b=3n+1
5(3n+1)+2=7c+3
15n+4=7c
c=2n+(n+4)/7
n+4=7m
n=7m-4
b=3n+1=21m-11
X=5b+2=105m-53
当m=1,最小的X=52可不可以用另一种方式写出来？设此数为X=3a+1=5b+2=7c+3所以a=(5b+1)/3=2b-(b-1)/3,因此b-1=3n, n为整数，即b=3n+1故5b+25(3n+1)+2=7c+3即15n+4=7c所以c=2n+(n+4)/7因此n+4=7m，m为整数故n=7m-4b=3n+1=21m-11此数为X=5b+2=105m-53当m=1,最小的X=52