(12/5-7/3)-(7/4-12/7)=12/5-7/3-7/4+12/7=(12/5+12/7)-(7/3+7/4)=1-1=0
(12/5-7/3)-(7/4-12/7)=12/5-7/3-7/4+12/7=(12/5+12/7)-(7/3+7/4)=1-1=0