Fasting on Mondays and Thursdays is better than fasting on three days of each month. If a person fasts on Mondays and Thursdays each week, that means that he is fasting eight days each month, so he will have done both. With regard to fasting on three days of each month, it is permissible to fast at the beginning of the month, in the middle or at the end, on consecutive days or separately. But it is better if it is done on the three white days, which are the thirteenth, fourteenth and fifteenth.

If ‘Ashura or ‘Arafah coincides with a Friday, you may fast because your intention is to fast ‘Ashura or ‘Arafah, not to fast on a Friday.