How many 12 Feet 2 x 4 would be needed for Bottom Plates and Double Top Plates on a Building 25' x 50' ?

Your question has confusing details. So, I will rephrase as:

How many 2' x 4' would be needed for Bottom Plates and Double Top Plates on a Building 25' x 50' ?

12.5 plates

Step-by-step explanation:

Given

Building dimension:

Plates

To do this, we have to divide the dimension of the building by the dimension of the plates

So, we have:

and

For the length, we have:

For the width, we have:

So, 12.5 of the plates are needed

or

step-by-step explanation:

we need to solve for 'x' the following equation:  

we have that:

⇒

⇒ ⇒

factorizing, we get that:

  ⇒

then, the solutions are: or

nothing extraneous has been found!