Final answer:
The equation that models the situation is d) x² - 6x - 28 = 0. The width of the frame is 7 cm.
Step-by-step explanation:
The equation that models the situation is d) x² - 6x - 28 = 0. To find the width of the frame, we need to solve this equation.
We can factorize the equation as (x-7)(x+4) = 0.
So, x = 7 or x = -4. Since the width cannot be negative, the width of the frame is 7 cm.