a) 17x12+17x18=
=17(12+18)=
=17x20=
=340
b)45x22+22x55=
=22(45+55)=
=22x100=
=2200
c)24x156+24x31-24x87=
=24(156+31-87)=
=24x100=
=2400
d)511x22+489x22=
=22(511+489)=
=22x1000=
=22000
e)67x377+377x33=
=377(67+33)=
=377x100=
=37700
f)12x13-13x2+13x90=
=13(12-2+90)=
=13x100=
=1300
