5.4×0.68+3.4×2×0.46=5.4x0.68+6.8x0.46=5.4x0.68+0.68x4.6=(5.4+4.6)x0.68=10x0.68=6.823.9—0.6×0.6-0.64=23.9-(0.36+0.64)=23.9-1=22.913÷12.5=(13x8)÷(12.5x8)=104÷100=1.047.8×4.86÷3.9=4.6x7.8÷3.9=4.6x2=9.2