a)
[tex]52-(30+12)=52-42=\boxed{10}\\\\26-(30-15):3=26-15:3=26-5=\boxed{21}\\\\36-6\cdot(12-7)=36-6\cdot5=36-30=\boxed6[/tex]
b)
[tex]42:(63-56)=42:7=\boxed6\\\\42:7+(63-29)=6+34=\boxed{40}\\\\100-14\cdot(6-2)=100-14\cdot4=100-56=\boxed{44}[/tex]
c)
[tex]2\cdot(103-93)=2\cdot10=\boxed{20}\\\\52-2\cdot(106-93)=52-2\cdot13=52-26=\boxed{26}\\\\84-(6\cdot12-42)=84-(72-42)=84-30=\boxed{54}[/tex]
