In a rectangle model, the vertical parts are (x) and (8), and the horizontal parts are (x) and (2). What is the total area?

Correct answer: x^2+10x+16

The direct answer is A. Add the vertical parts to get the total height x+8, and add the horizontal parts to get the total width x+2. The rectangle’s area is therefore (x+8)(x+2). Multiply each part: x times x=x^2, x times 2=2x, 8 times x=8x, and 8 times 2=16. Adding gives x^2+2x+8x+16=x^2+10x+16. B incorrectly swaps the coefficient of x and the constant term. C uses 6x, although the two cross-products add to 10x. D lists only the original boundary parts and omits the complete multiplication. A reliable check is to add the four small rectangle areas rather than trying to guess the expanded expression.