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First, solve the "perimeter" equation
(2x-2) + (-2x+18) + (7x-27) = 24.
2x - 2x + 7x + (-2 +18 - 27) = 24
7x - 11 = 24
7x = 24 + 11
7x = 35
x = 35/7 = 5.
Thus the side lengths are 2x-2 = 2*5-2 = 10-2 = 8;
-2x+18 = -2*5+18 = -10+18 = 8;
7x-27 = 7*5-27 = 35-27 = 8.
Thus you have an equilateral triangle.
The triangle inequalities are held by an OBVIOUS way.
Solved.
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The sequence of actions that @josgarithmetic proposes in his post is WRONG.
You DO NOT NEED check the triangle inequalities BEFORE finding the side lengths.
You need check these inequalities AFTER finding the triangle' side lengths.
So, for your safety, you better IGNORE the post by @josgarithmetic.