We start by looking at one part of the expression 16. This subexpression can be simplified since 16=44=42 which gives that 16=42=4 and the whole expression becomes
16+16=16+4=20.
Can 20 be simplified? In order to answer this, we split 20 up into integer factors,
20=210=225=225
and see that 20 contains the square 22 as a factor and can therefore be taken outside the root sign,
16 
4=42
42=4 
16+
5=2