The square part has an area of 10 * 10 = 100 square cm. The base of the triangle is 5. From your drawing I assume that the height of the triangle (next to the square) is 5.4 cm. If so, then the area of the triangle is base (5) times the height (5.4) divided by 2. This would be equal to 5 * 5.4/2 = 13.5 square cm. Therefore, the total area is

100 + 13.5 = 113.5 square cm. Let me know if I have misinterpreted the diagram.