First thing first,you need to understand the symbols:
> means the value is larger than the other value
< means the value is smaller than the other value
= means the value is equal to the other value
We could then look into the questions,which requires the changing of units:
1. 17.1g (17100mg) > 1.71mg, as 1g = 1000mg
2. 6.3 cm(63mm) = 63mm, as 1cm = 10mm
3. 1250 ml < 12.5kL (12500000ml), as 1kL=1000000 mL
4. 7/12 < 2/3, as 2/3= 8/12
5. 7/10 < 11/15,as 7/10=14/30 and 11/15=22/30
Hope it helps!