That's OK. You have calculated it correctly, just your use of symbols is somewhat twisted
[Ca
2+ ] usually means "concentration of Ca
2+ cations", thus below equations look strange:
Ca(OH)2 <-----> [Ca2+] [OH-]2
NaOH ------> [Na+] [OH-]
These are neither formulas for K
so nor balanced reaction equations.
And you don't have to use some [x ] notation, as you are solving just for [Ca
2+ ].