Longarekel: the rashi that says each makka was a quarter of a month is not in shemos 8, 25 but in shemos 7,25 which is based on that pasuk that says 7 days.
NEW QUESTION: From where do we know that one getting married should check out the kalla’s brothers? You must bring a source! (Clue: Its not Lavan – unless you find a source. I couldnt find the source with lavan but found the source someplace else).