If the sum of two sides of a triangle is 21 cm and its perimeter is 35 cm, then what is the length of the third side?
Two sides of a triangle are 12 cm and 14 cm. The perimeter of the triangle is 36 cm. What is its third side?
The perimeter of a triangle with two sides of length 15 cm and 12.5 cm is 40 cm. Its third side is