9514 1404 393
Answer:
8 ft
Step-by-step explanation:
Let t represent the length of the third side. The first side is 7 ft more, so is (t +7). The second side is 1 ft shorter than 3 times the third side, so is (3t -1). The perimeter is the sum of the side lengths:
21 = (t +7) +(3t -1) +t
21 = 5t +6
15 = 5t . . . . . . . subtract 6
3 = t . . . . . . . divide by 5
Then the length of the second side is ...
3t -1 = 3·3 -1 = 8 . . . . feet
The length of the second side is 8 feet.
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<em>Additional comment</em>
The first side is 3+7 = 10 ft. So the three side lengths are 10 ft, 8 ft, 3 ft.
