Concept:An isosceles triangle has two equal sides, and the perimeter is the total length around the triangle.Explanation:Let the third side be x cm.Each equal side is 14 cm.So the perimeter is the sum of all three sides:45=14+14+x45=28+xSubtract 28 from both sides:x=45−28x=17Therefore, the third side measures 17 cm.Answer:C. 17 cm