Two sides of a triangle have the same length. the third side measures 7m less that twice the common length. the perimeter of the triangle is 17m. what are the lengths of the three sides?

A formula you can use to solve this problem is:

2x + (2x-7) = 17

The first 2x represents the two sides that have the same length, the (2x-7) represents the side that is 7m less than twice the common length, which altogether equal 17m, the perimeter.

From there, solve for x:
2x + (2x-7) = 17
4x - 7 = 17
4x = 24
x = 6

So two sides are 6m. The third side's length can be determined with 2x-7, so it is 5m.