3/5 + (4/5 3/7) + 6/7
= 3/5 + 12/35 + 6/7
= 3/5 + 12/35 + 30/35
= 3/5 + 42/35
= (37 + 42) / 35
= (21 + 42) / 35
= 63/35
= 9/5