In general you would need to select a vertex of the nonagon and join it to the other vertices (except the two adjacent ones). This will divide the nonangon into 7 triangles. Measure the sides and/or angles of these triangles and calculate their areas. Add these together to get the area of the nonagon.
If the nonagon is regular then there are formulae to calculate its area. These depend on whether you know the side length, apothem or circumradius.
You add together the lengths of the nine sides of the nonagon.
The area is 1583 square units, approx.
Approx 566.9 square inches.
A regular nonagon with a side length of 9 has an apothem of 12.4 not 16. So the question is inconsistent.
nonagon
It is a plane area in the shape of a nonagon!
Area of a nonagon with a circumradius of 2 units is 11.57 square units.
A nonagon is a plane area enclosed by nine straight lines.
The area is indeterminate, since the shape can be a long thin nonagon with minimum area or a regular one with maximum area.
First you must determin what the "apothem" is, and by that i mean what the hell that word means.
Some pools are made in the shape of a nonagon. The Baha'i House of Worship in Wilmette, Illinois is also a nonagon.
You add together the lengths of the nine sides of the nonagon.
The area of a rectangle does provide enough information about its dimensions. It is possible fo the rectangle to be long and narrow or squat and short (almost square).
The area is 1583 square units, approx.
396 ft
It is 72.3 square units, approx.
Approx 566.9 square inches.