Let x = 0.2166....
.'. 100x = 21.66... ---> 1.
.'.1000x=216.66..... ---> 2.
Let, 2 - 1
900x = 195
.'. x = 195/900
.'. x = 13/60
Here you dont have to worry about subtracting a negative make sure only the recurring decimal is on the right hand side of the decimal. =D