2 5/6 - (1 5/9 + 1/4)=-1 1/3
1 5/9+1/4=14/9+1/4=56/36+9/36=65/36
2 5/6-65/36=17/6-65/36=-48/36=-1 1/3
7/20-(3 5/8 - 3 2/5)=1/8
3 5/8 - 3 2/5=29/8-17/5=145/40-136/40=9/40
7/20-9/40=14/40-9/40=5/40=1/8
3/4-(4/25 + 7/20)=0.24
4/25+7/20=16/100+35/100=51/100
3/4-51/100=75/100-51/100=24/100=0.24