Answer
See below.
Work Step by Step
From part a) the area is: $x^2+5x+6$.
$x^2$ is the blue area. We have $5$ green areas each with area $1\cdot x=x$. We also have $6$ yellow areas each with area $1$. These three "colors" of areas sum up to $x^2+5x+6$ as required.
