can I upgrade inspiron 3558 laptop RAM from 8GB to 16GB, is it supports 16gb?
I want to know whether it has two slots to fit two 8GB RAMs
Yes - you'll need 2x8G, DDR3L soDIMMs.
may I know if there are two slots for Inspiron 3558
There are two memory slots, yes.
can I add 16 gb in one slot and 4 gb in 2nd or only support it upto 16 gb
The system supports up to 2X8 modules - not a single 16.