a) [(9+3x7) - 2 x4+2x11]:4= b) [(4x12-8)+(13x5-5):12=

[(9/1+3/1x7/1)-2/1x4/1+2/1x11/1)]:4/1=[(9/1+21/1)-8/1+22/1)]:4/1=[30/1]-30/1:4/1=0:4/1=0x1/4=0 ](4/1x12/1-8)+(13/1x5/1-5/1):12/1=(48/1-8/1)+(65/1-5/1):12/1=(40/1)+(60/1):12/1=100/1:1/12=25/3=8 1/3