We have,
∠A = ∠CED
In ΔCAB and ΔCED
∠C = ∠C(common)
∠A = ∠CED(Given)
Then, ΔCAB ~ ΔCED (By AA similarity)
So,\(\frac{CA}{CE}\) =\(\frac{AB}{ED}\) (Corresponding parts of similar triangle area proportion)
Or,15/9 = 9/x
Or, 15x = 90
Or, x = 90/6
Or, x = 6cm.