To solve this problem you must apply the proccedure shown below:
1- The formula for calculate the area of this rectangle is:

Where
is the length and
is the heigth.
2. Let's call identify the heigth with the variable
.
3. If the length is
longer than the heigth, you have:

4. Therefore, you can write the following polynomial expression:

5. If you know the value of the heigth, you can susbstitute it into the polynomial expression shown above and you will obtain the area.
Therefore, the answer is: 
Arc length = radius * central angle (in radians)
central angle = arc length / radius
central angle = 7 / 7
central angle = 1 radian
central angle = 57.296 degrees
First term is 2 and the common difference is the value by which it increases which is 2.
4 x -5 = -20 then 12 + -20 = -8