1. As you can see in the figure attached, the area of the photograph is:
 
 A=LxW
 
 A is the area of the photograph (A=54 in²).
 L is the lenght of the photograph (L=12-4x).
 W is the widht of the photograph (W=12-2x)
 
 When you substitute these values into the formula A=LxW, you obtain:
 
 A=LxW
 54=(12-4x)(12-2x)
 
 2. Now, you must apply the distributive property. Then:
 
 54=144-24x-48x+8x²
 8x²-72x+144-54=0
 
 3. Therefore, you obtain a quadratic equation for the area of the photo:
 
 8x²-72x+90=0
 
 The answer is: 
 
 8x²-72x+90=0