Answer:
[tex]x^2+15x+36[/tex]
Step-by-step explanation:
The complete question is shown in the attachment.
The length of the rectangle is x + 12. The width of the rectangle is x + 3.
Recall that area of a rectangle is [tex]Length \times Width[/tex]
In terms of x, the area is [tex](x+12)(x+3)[/tex]
Recall the distributive property of real numbers: [tex](a+b)(c+d)=a(c+d)+b(c+d)[/tex]
We apply this property to get:
[tex](x+12)(x+3)=x(x+3)+12(x+3)[/tex]
We expand again to get:
[tex](x+12)(x+3)=x^2+3x+12x+36[/tex]
We now simplify to obtain:
[tex](x+12)(x+3)=x^2+15x+36[/tex]
The area of the rectangle is [tex]x^2+15x+36[/tex]