Answer:
Ok so the area of the frame is 18*12 = 216cm^2
Let’s suppose the width of the frame is x
The total area (painting and frame) is (2x+18)(2x+12) and this is equal to 432
4x^2 + 60x + 216 = 432
4x^2 + 60x - 216 = 0
x^2 + 15x - 54 = 0
(x+18)(x-3) = 0
Therefore x = {-18,3}
Since width of the frame has to be positive, the width has to be 3cm Step-
i hope i helped!