when i want add platform android i get error
ionic info
i test below command
npm install
npm install -g ionic & cordova
I once had this issue I downgraded my cordova version
npm install cordova@6.5.0
I hope it helps.
tnx for answer but not worked for me
zatea tnx i test again but with below code
npm install -g cordova@6.5.0
and worked for me 
only small extra hint:
With Windows I know also it always good to start the console (cmd) as administrator.
yes. i start ad admin 
No, it emphatically isn’t.
There is never any need for running npm or ionic or cordova with elevated privileges, on any OS, and when you do so even once, you are likely to mess up permissions all over the place in a way that is difficult to clean up afterwards.
Use nvm or nvm-windows to manage your node installations instead.