Answer:
The length of the model is 21 inches
Step-by-step explanation:
we have
The scale factor

That means
1 unit in the model represent 12 units in the actual
1 inch in the model represent 12 inches in the actual
Remember that

so
1 inch in the model represent 1 ft in the actual
The scale factor is

therefore
21 ft in the actual represent 21 inches in the model
A calculator can help you with that.
In radians, arcsin(sin(9π) / 7) = 0.
I think you are yousing to much lectrsestey