A karate studio charges $35 for the first course and $22.50 for each course after that, even if the student leaves the course early. Cena paid $170 for her son to take courses. How many courses did he take?

The first course costs $35, leaving $170 − $35 = $135 for the additional courses. At $22.50 each, that covers $135 ÷ $22.50 = 6 additional courses. Including the first course, he took 6 + 1 = 7 courses, so the answer is B, 7 courses.

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