Given
The diagonal ratio is given AC:FD=7:5.
The length of AG is 3cm.
Step-by-step explanation
To find CE.
The diagonals ratio is same as the side of square ratio.
Reason-
The diagonals are the square root of 2 multiply by side.

D denotes the diagonal and S denote the side, of suare.
So, the ratio of diagonal is same as the ratio of sides of square.

Here D and d denotes the diagonal of the squares and s and S is the sides of squares.
Let AD = 7x , GD = 5x

Now find the length of CE,

Substitute the value of x in the CE.

Answer
Hence thelenghth CE is 18cm.