Answer:
variable, In algebra, a symbol (usually a letter) standing in for an unknown numerical value in an equation. Commonly used variables include x and y (real-number unknowns), z (complex-number unknowns), t (time), r (radius), and s (arc length).
First, divide the the polygon into two quadrilateral.
Then find the area of both quadrilaterals
The area of the small rectangle = 4 x 3 = 12 square feet
The area of the bigger rectangle = (9 - 3) x 14 = 6 x 14 = 84 square feet
Add both areas:
12 + 84 = 96 square feet
600x1.07^11 = 1262
11 Months

which follows from the usual change of coordinates via

and Jacobian determinant

Swap the order, so that the integral is

and now let

, so that

. Now, you have