If you expand the square, you have

Simplify the right hand side:

Cancel the -3x appearing on both sides:

Multiply both sides by 4:

Consider the square root of both terms (using the doubles sign):

Answer:
Area = 406
Step-by-step explanation:
First things first: Divide the shape
Here is how I did it:
21 x 16
14 x 5
Now solve:
21 x 16 = 336
14 x 5 = 70
Now add:
336 + 70 = 406
So the area is 406
Her speed was 62.5 miles per hour.
The directions say round to the nearest tenth so use the 8.8 cm