a) 425.7.4-170.60
=85.5.7.4-85.2.60=85.(5.7.4-2.60)=85.20=1700
b) 8.9.14+6.17.12+19.4.18
=72.14+72.17+72.19=72.(14+17+19)=72.50=3600 
b: \(8\cdot9\cdot14+6\cdot17\cdot12+19\cdot4\cdot18\)
\(=72\left(14+17+19\right)\)
\(=72\cdot50=3600\)
a, 425 x 7 x 4 - 170 x 60
=> 85 x 5 x 7 x 4 - 85 x ( 5 x 7 x 4 x 2 - 60 )
=> 85 x 20
=> 1700
b,8 x 9 x 14 + 6 x 17 x 12 + 19 x 4 x 18
=> 72 x 14 + 72 x 17 + 72 x 19
=> 72 x ( 14 + 17 + 19 )
=> 72 x 50
=> 3600
