An isosceles triangle has two sides of equal length. the third side is 5 less than twice the length of one of the other sides. if the perimeter of the triangle is 23 cm, what is the length of the third side?

explain how you would define a variable for this problem.

Let's take one side of the two equal lengths as r
third side is s.
so the total perimeter is r + r + s
2r + s = 23

According to the statement of third side s, 
5 less than twice the length of one of other
s = 2r - 5

we have 2 equations and 2 unknowns. so we can find out the values of those letters.

2r + s = 23
2r - s = 5

4r = 28
r = 7

s = 9
Therefore the third length will be equal to 9 cm.

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