Short Answer 
Linda’s expression contains both correct and incorrect terms for calculating the attic’s surface area, identifying the accurate term as 45(40 + 25 + 25). The second term needs adjustment by adding a factor of 2 to become 8(40 x 15), ultimately leading to a correct total surface area of 4650 square feet after summing the revised expressions.
Step 1: Identify the Correct Terms
The expression that Linda drew has a part that is accurate and another that needs adjustment. The first term, 45(40 + 25 + 25), reflects the correct sum, representing some of the attic’s dimensions. Knowing what is correct helps in assessing what needs revision in her calculation.
Step 2: Correcting the Missing Factor
Linda’s second term, 4(40 x 15), actually requires an additional factor of 2 for accuracy. This means the complete term should be 8(40 x 15), which accounts for the physical dimensions properly. Ensuring all dimensions are represented is crucial for calculating the surface area accurately.
Step 3: Calculate the Surface Area
After correcting the expression, evaluate the total surface area of the attic. Linda’s final calculation yields a surface area of 4650 square feet. This final result can be reached by summing all corrected terms from her expression, confirming the validity of these figures through proper computation.