Bug fix/character encoding

The fix ended being: just resave existing ArithmeticQuestion with UTF-8 encoding in the project itself. That ended up fixing those ?? characters. It looks like when the symbols ÷ and × got saved into ArithmeticQuestion.java they were not saved as UTF-8. It appears that saving locally ArithmeticQuestion fixed the problem. However, in the PR and commits this is not directly reflected. Anyways, the problem is fixed now and on device/emulator it looks fine.