a=[(20* 25^200)*(2^200*10^3)] : (2^100*5^400*250)=
=[(2^2*5* 5^400)*(2^200*2^3*5^3)] : (2^100*5^400*5^3*2)=
=[(2^2*5^401)*(2^203*5^3)] : (2^101*5^403)=
=(2^205*5^404)*) : (2^101*5^403)=
=2^104*5
b=(6+2)*[(3*5^2-2^2*18: 3^2+ 3*11) : 2]=
=8*[(3*25-8+ 33) : 2]=
=8*[(75+ 25) : 2]=
=8*(100 : 2)=
=8*50=400