Answer:
21.42 cm
Explanation:
Perimeter is just the sum of all of the side lengths.
Before you can do that, though, you need to figure out what the rounded side would be.
Imagine for a moment that the rounded area is a full circle, and find the perimeter or, in this case, circumference, of that. The formula to find this is
where r = radius. You can see that the radius is 3, so plug that into the equation and solve (we are using 3.14 instead of pi)

c = 18.84
Since we don't actually have the entire circle here, cut the circumference in half. 18.84/2 = 9.42
The side length of the rounded area is 9.42
Now, we just need to add that length to the side lengths of the rectangular part, and we will have our perimeter.

The perimeter of the figure is 21.42 cm.