Let the Length of equal sides of an isosceles triangle be x cm.
Perimeter of a triangle = Sum of all three sides
⇒4215=43+x+x
⇒6215=43+2x
⇒6215−43=43−43+2x
[Subtracting 43 from both the sides]
⇒62−2015=2x
⇒4215=2x
⇒4215×2=2x2 [Dividing both sides by 2]
⇒75=x
⇒x=125cm
Hence, each equal side of an isosceles triangle is 125cm.