5/21x2/7+219/21x5/7+(1-2/7)

5/21x2/7+219/21x5/7+(1-2/7)
=5/7*2/21+5/7*219/21+5/7
=5/7*(2/21+219/21+21/21)
=5/7*242/21
=1210/147
这题出得不好，最后应该可以化简才有意义。

(10+219*5+3*21)/(7*21)

题目并不难！但是不得不感叹现在的出卷教师真是会折磨人！

5/21x2/7+219/21x5/7+(1-2/7)
=(5x2+219x5)/(21x7)+5/7
=(5/7)x[(2+219)/21+1]
=(5/147)(221+21)
=(5*242)/147
=1210/147