Luisa mows lawns during the summer. She charges $15 if she cuts the grass but charges $5 more if she also trims the grass. Last week she trimmed 5 more yards than she cut. If she made $415 last week, how many yards did she trim?

Well, those 5 extra yards had given her an extra $100, so the yards she cut, plus those she trimmed, had given her $315. To cut one and trim another one she takes $35. This means 9 yards were cut and 14 trimmed. (do a division, 315/35=9).