Answer:
The area of a rectangle is length times width.
First recall the answer gives you x=4.2 for the eqaution x+5.8 and for the length.
Input that into the rectangle´s area formula.
(4.2)(4.2+5.8)
(4.2)(10)
=42 units^2.
Now to find the perimeter you need to add all the sides. We have two lengths and two widths.
4.2+4.2+10+10
= 28.4
Explanation:
If you want more explanations then Khan academy is a great source.