Answer:
2x² + 12x
Step-by-step explanation:
Area of rectangle:
  Area of rectangle = length * width
Poster 1:
    length = x inches
    widht = (x + 5) inches
Area of poster 1 = x * (x + 5)
              = x*x + x*5   {Distributive property}
              = x² + 5x square inches
Poster 2:
   length = x inches
    width = (x + 7) inches
Area of poster  =x *(x+ 7)
            = x*x + x*7
            = x² + 7x
Area of wall = area of poster1 + area of poster 2
          = x²+ 5x + x² + 7x
          = x² + x² + 5x + 7x   {Combine like terms}
          = 2x² + 12x