If one side of the square is 8 cm, that makes the area of the square 64 cm², because you just square a side to get the area of a square. A circle's area is π r², but this is a quarter circle, so it'll be 1/4 πr². The radius of this quarter circle is 8 cm, since it shares the side with the square. 1/4 π(8)² = 50.24 cm². Add the two areas together to get a combined area of 114.24 cm² for this figure. This is an approximation because pi (and therefore the area of the circle) is approximated.
Make sense?