Answer:
42 square inches.
Explanation:
The given expression for the area of the triangular sail is

Here b is the length of the base and h is the height.
Now, we have to find the the area of a triangular sail in a model sailboat when b=12 inches and h=7 inches.
Substituting these values in the above expression to find the area of the triangular sail.

Therefore, the area of triangular sail in a model sailboat when b=12 inches and h=7 inches is 42 square inches.