3/5 - 1/7
Find the LCM of 5 and 7 to find equivalent fractions for both fractions
LCM = 35
3/5 = 21/35
1/7 = 5/35
So 21/35 - 5/35 = 16/35
I'm pretty sure that's the simplest form because I can't think of a common factor of 16 and 35 by which to reduce it further.