Answer:
9 weeks
Explanation:
If she took 10 quizzes over the span of 5 weeks, then she took 2 quizzes per week.
This is because:
10 quizzes ÷ 5 weeks = 2 quizzes
We can use this information to solve for 18 quizzes by setting up the equation the same way
If she takes 2 quizzes every week, and ends with 18 finished quizzes, how many total weeks did it take her ?
Variable x = total weeks
18 quizzes ÷ x weeks = 2 quizzes
With division, we can switch x weeks and 2 quizzes
18 quizzes ÷ 2 quizzes = x weeks
18 ÷ 2 = 9
9 weeks