Hi Chinmoy,

The sum of the interior angles of a triangle is $180^o$ and since you know the measures of two of the angles you can calculate the measure of the third.

When I see a question like this about the angles and side lengths of a triangle I think of the Law of Sines and the Law of Cosines. Which one of these will allow you to determine the lengths of the other two sides? Why do I want the lengths of the three sides? Because I can use them and Heron's Formula to calculate the area of the triangle.

Harley