Final answer:
The length of the porch is 15 feet and the width is 8 feet.
Step-by-step explanation:
To find the length and width of the porch, we need to set up an equation using the given information:
Area = length x width
120 = (x + 12)(x + 5)
Expanding the equation: 120 = x^2 + 17x + 60
Setting the equation equal to zero: x^2 + 17x - 60 = 0
Factoring the quadratic equation: (x + 20)(x - 3) = 0
Solving for x: x = -20, x = 3
Since the dimensions of the porch cannot be negative, we can conclude that x = 3.
Therefore, the length of the porch is x + 12 = 3 + 12 = 15 feet, and the width is x + 5 = 3 + 5 = 8 feet.