The perimeter of the triangle is 80 cm. One side is 27 cm, and the other is 34 cm. Find the length of the third side.

The perimeter of a triangle has the following formula:
P = a + b + c, where a, b and c are the sides of the triangle.
Let’s say a = 27 cm, and b = 34 cm, then we just have to find side c. Let’s express it from the previous formula:
c = P – (a + b).
First, find the sum of sides a and b:
a + b = 27 + 34 = 61 cm.
Now let’s find side c:
c = 80 – 61 = 19 cm.
Answer: The length of the third side of the triangle is 19 centimeters.