Answer:
x = 10
Explanation:
Since the pentagons are similar you can say...
4x cm/48 cm = x cm/(x+2) cm
Now do cross multiplication with this equation, so 4x is multiplied with (x+2) and 48 is multiplied with x... you end up with:
4x^2+8x = 48x, now subtraction 8x from 48 x....
4x^2 = 40x, and divide one x from each side
4x = 40, therefore x = 10