a) 12⋅43−203⋅4512⋅43−203⋅45

=\(\dfrac{2}{3}\)
−\(\dfrac{16}{3}\)
=23−163

=\(\dfrac{-14}{3}\)
=−143 ;

b) 37+−619+47+−131937+−619+47+−1319

=(37+47)+(−619+−1319)=(37+47)+(−619+−1319)

=77+−1919=77+−1919

=1+(−1)=0=1+(−1)=0 ;

c) 35⋅89−79⋅35+35⋅26935⋅89−79⋅35+35⋅269

=35⋅(89−79+269)=35⋅(89−79+269)

=35⋅279=35⋅279

=35⋅3=35⋅3

=95=95.