(1)275+450÷18×25 =275+25×25=275+625=900;(2)5× 1 3 × 3 5 × 3 10 = 5 3 × 3 5 × 3 10 = 3 10 ;(3)31×101 =31×100+31×1=3100+31=3131;(4)12×( 3 4 + 1 6 - 1 3 )=12× 3 4 +12× 1 6 -12× 1 3 =9+2-4=11-4=7.