Question

how 21 came in this question two equal sides of a triangle are each 5 metres less than twice the third side if the perimeter of the triangle is 55 meters find the length of its side

Answer 1

In geometry, an isosceles triangle is a triangle that has two sides of equal length. Sometimes it is specified as having two and only two sides of equal length, and sometimes as having at least two

Answer 2

Let the length of third side be x m. Then,
the length of the two equal sides will be (2x−5) m.
∴(2x−5)+(2x−5)+x=55
⇒2x−5+2x−5+x=55
⇒5−10=55
⇒5x=65
⇒x=65/5=13
∴Length of the third side=13 m
And length of the other two equal sides=(2×13)−5=21 m