Because the width is 3/7 of 21, we can multiply 3/7 by 21 to find the width. 3/7 * 21 = 9. So, the width is 9.
Now we know that the width is 9 and the length is 21. From this, we can find the perimeter and area of the rectangle. The perimeter is equal to 9 + 9 + 21 + 21 = 60. So, the perimeter is 60 inches.
Now, we need to find the area. We do this by multiplying 21 * 9. This is equal to 189, so the area is 189 square inches.