Keyboard is not responding?
Some of the keys do not type.
The Asus X200CA laptop is 11.6 inches and weighs 2.6 lbs. It comes with a either an Intel® Core™ i3 3217U Processor, an Intel® ULV Pentium® 2117U Processor, or an Intel® Celeron® 1007U Processor, 2 GB or 4 GB of RAM, 320 GB to 1 TB of storage, Windows 8 OS, HD webcam, and an estimated battery life of 3 hours.
Fixing individual keys is not usually possible, but a complete new keyboard is not that expensive and quite easy to fit. Make sure you get one of the right nationality (US, UK etc as appropriate) and do a google search for Asus X200CA keyboard replacement for a guide. From a quick glance it looks like there are one or two screws on the bottom of the laptop that you have to remove, then there are a few tabs, probably along the top of the keyboard, that you have to release with a spatula or thin knife to allow the keyboard to be lifted out.
Keys are Stuck
There might be crumbs stuck inside your keyboard. Try holding your laptop upside down or at a 45 degree angle from being horizontal and give it a few good shakes that will dislodge anything stuck between your keys. Use a keyboard vacuum or a can of compressed air, these can help to remove any particles in between the keys interfering with its usability.
The ribbon cable connected to the keyboard may have come loose. Fix this by reconnecting the cable.
If you spilled any liquids, especially soda that can get sticky when dried, apply some cleaning solution, such as rubbing alcohol or soapy water, to a dish towel and gently rub down the affected keys. You can also remove keys and wipe it from the inside.
If those methods are not applicable, try rebooting your computer. If none of these work, try replacing the keyboard.