x= sides of square (all sides are equal)
(x-3)= length of rectangle
(x-4)= width of rectangle
Area of rectangle= length x width
A= (x-3)(x-4)
multiply each term in the left parentheses by each in the right
A= (x*x) + (x*-4) + (-3*x) + (-3*-4)
A= x^2 -4x -3x + 12
combine like terms
A= x^2 -7x + 12 Area of the photograph
Hope this helps! :)
