500
Carlos has a large box of donuts with enough donuts to last 21 days. If Carlos eats only one donut every morning, how many weeks will the box of donuts last?
A 1 week, because 21 ÷ 21 =1
B 21 weeks, because 21 ÷ 21 =1
C 3 weeks, because 21 ÷ 7 = 3
D 7 weeks, because 21 ÷ 3 = 7
What is 3 weeks because 21 ÷ 7 = 3 (C) ?