[Modify exercise]
modify the case3 in repeated_addition.html
[temp modify]
there is a problem in case1. The "num" is randRange(1,2), but it would be 3.
[RM case]
Remove caseD1 and caseD2 in place_value_big_number.html
[rm repeated_addition.html]
Remove repeated_addition.html
Merge branch 'place_value_big_number'