Respuesta :

Answer:

[tex]40 \:mm[/tex]

Step-by-step explanation:

An equilateral triangle has 3 equal sides.

[tex]\frac{120}{3} =40[/tex]

Answer:

40mm

Step-by-step explanation:

Perimeter of an equilateral=3a

120=3a

a=120/3

a=40mm