The memory type is listed as:
8GB DDR3L SDRAM
There is no information on how many slots the laptop has, nor if it will support anything more than the 8GB it has now. They do not even offer memory as an upgrade, [strike]which kind of leads me to believe that 8GB is probably the limit.[/strike]
As I often do when I cannot find out what something like your notebook has for memory from the manufacturer, I go to Crucial.com. Their parent company, Micron Technologies, owns memory fabs, so they really know memory.
Your ASUS K501LX
Maximum memory: 12288MB
Slots:1 (1 bank of 1)
So it looks like you have one memory slot. Despite listing 12GB as the maximum that your notebook can have, the highest capacity memory sticks they offer are 8GB.
So that is probably what you are stuck with.
If you are interested, they do show 2 SSD's...
Crucial BX100 120GB SATA 6Gb/s 2.5" Internal SSD
Crucial BX100 500GB SATA 6Gb/s 2.5" Internal SSD