Answer
$x^{2} + 2x$
Work Step by Step
1. Area of the vertical rectangle
$= width \times length$
$= [(x+3)-(x)] \times (x)$
$= (3) \times (x)$
$= 3x$
2. Area of the horizontal rectangle
$=width \times length$
$= (x) \times (x-1)$
$= x^{2} - x$
3. Total area
$= 3x + x^{2} - x$
$= x^{2} + 2x$
