To determine the area of the remaining paper, you have to subtract the area of the semicircle ( i.e. the area of a full circle) from the area of the rectangle.
Recall that the area of a circle is given by the following formula:
[tex]A_c=\pi r^2,[/tex]where r is the radius. Now, the semicircles have a radius of 12cm/2=6cm, therefore, the area of the circle formed by the semicircles is:
[tex]Ac=\pi(6cm)^2=3.14(36cm^2)=113.04cm^2.[/tex]The area of a rectangle is given by the following formula:
[tex]A_r=wl,[/tex]where w=width, and l=lenght. Therefore, the area of the rectangle is:
[tex]A_r=(24cm)(12cm)=288cm^2.[/tex]Finally, the area of the remaining paper is:
[tex]288cm^2-113.04cm^2=174.96cm^2.[/tex]