a.156*75+25*150
=156*25*3+25*150
=25*(156*3+150)
=25*618
=15450
b,791*101-791
=791*101-791*1
=791*(101-1)
=791*100
=79100
c,2*15*4*25
=(2*15)*(4*25)
=30*100
=3000
\(794\times101-794\)
\(=794\times\left(101-1\right)\)
\(=794\times100\)
\(=79400\)
\(2\times15\times4\times25\)
\(=\left(2\times15\right)\times\left(4\times25\right)\)
\(=30\times100\)
\(=3000\)