Answer:
6
Explanation:
You have to insert each of the numbers in place of n and do the equation to see if it adds up to 78.
2(6) + 1 = 78
the others do not equal 78, therfore n = 6
D 6
Area = L × W
(2n + 1)(6) = 78
(6 × 2n) + (6 × 1) = 78
12n + 6 = 78
12n = 78 - 6
12n = 72
n = 72/12
n = 6 cm
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