(1) 3 4 ×( 4 3 - 8 9 )= 3 4 × 4 3 - 3 4 × 8 9 =1- 2 3 = 1 3 ;(2)1÷[( 1 6 + 1 3 )÷4]=1÷[ 1 2 ÷4]=1÷ 1 8 =8;(3)0.25×0.07×8=0.25×8×0.07=2×0.07=0.14;(4)6.8×10.7-0.7×6.8=6.8×(10.7-0.7)=6.8×10=68.