Can someone me with this algebra question 100% correct only

The answer is:  [D]:  " 24 + 2w " .

Explanation:

Given: The formula for the Perimeter of a rectangle:

   P = 2L + 2w ; 
  
                 in which:
                                P = perimeter ;
                                L = length = 12 units (given); 
                                w = width = unknown;

           Find the perimeter, "P", in terms of "w" ; since "w" (width) is unknown; and considering the answer choices given; along with the information provided in the problem, we only have enough information to solve for the perimeter, "P", in terms of "w" ; 

         So, given the formula/equation for the perimeter, "P" :

       P = 2L + 2w ;  we know that:  " L = 12 units " ;

       P = 2*12  +  2w  =  24 + 2w ;  which is:  "Answer choice: [D]" .

Num of plants = (original#ofplants)*(1.6)^t