五年级数学上册解复杂的方程练习12x-8x=4.8 3.5-5x=2 5x-2x+18=78 x-0.7x=3.6 9.8-x=3.8 5x-45=100 4.5(x-2.5)=27 0.75+0.25x=1.257(6.5+x)=87.5 9x-x=16 6-2x=11 5x-22.5=201.5(x+1.6)=3.6 805x=100 917x 1.3 (200-x)5=30 (x-140)70=4 75.6x=12.6 (27.5-3.5)1.5x=4 45x=205448x=18x60 53x=17.6x5x2=7x8