The answer is 78 feet of fencing. This is because you need to find the perimeter of the yard. To find the perimeter of the yard, you add the sides together, so 21+21+18+18 = 78.
Answers: Choice A and Choice C
Saying "$45 per ticket" is the same as saying "$45 for every single ticket" or "one ticket costs $45"
Similarly, "30 seats for every row" is equivalent to "each row has 30 seats"
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choices B and D aren't unit rates because the second value mentioned isn't 1. You would have to divide to get to a unit rate.
choice B: 5/3 = 1.67 so there are roughly 1.67 shows every week
choice D: 100/5 = 20 meaning its $20 per ticket
