Abuilder is installing a norman window made up of a rectangle topped by a semicircle. if the radius of the semicircle is r, and the rectangle is 3r high, find the area of the window as a function of r.

Notice the picture

the semicircle, has a radius of "r",  you can use that to get the area of a circle, then half it, that's the area of that semicircle in "r" terms,

now, look at the rectangle the semicircle is sitting on top of, to make up
the normal window, it has a height of 3r, and notice its width

so, get the area of the semicircle, and the area of the rectangle,
both in r-terms
add them up, and that's the area of the window