Area is calculated by multiplying length by width. Since we are given the width, we can test each length and see if the product matches the rectangle's area.
(2m - 3)(4m - 4) = 8m² - 20m + 12 ≠ 8m² + 4m - 12
(8m - 3)(4m - 4) = 32m² - 44m + 12 ≠ 8m² + 4m - 12
(2m + 3)(4m - 4) = 8m² + 4m - 12
(8m + 3)(4m - 4) = 32m² + 20m - 12 ≠ 8m² + 4m - 12
The length of the rectangle must be 2m + 3. Another method of solving this would be to divide the area by the width, or 8m² + 4m - 12 ÷ 4m - 4.