The perimeter of triangle LMN is calculated by adding the lengths of all three sides of the triangle. If the lengths of the sides are given as follows: LM = a, MN = b, and NL = c, then the formula for the perimeter (P) can be expressed as:
P = a + b + c
For example, if the lengths of the sides are LM = 5 units, MN = 7 units, and NL = 3 units, the perimeter would be:
P = 5 + 7 + 3 = 15 units
Therefore, you simply need to measure the lengths of the sides of triangle LMN and apply the formula to find the perimeter.