Perimeter Formula:

Area Formula:

Set perimeter Formula equal to b:

Plug formula for be we just made above into the area Formula:

Solve for L (you'll have to use quadratic formula) then plug that back into the area Equation and solve for b.
Here's a link to where the problem has been explained before (they go into more detail than me).
https://brainly.ph/question/468631
lmk if you need any more help
Answer:
Vertically Opposite Angles are the angles opposite each other when two lines cross "Vertical" in this case means they share the same Vertex (corner point), not the usual meaning of up-down.
Step-by-step explanation: