先把1.8右移,得x/2=3.9-1.8,即x/2=2.1然后两边同时乘以2得,x=2.1*2,即x=4.2x*2+1.8=3.9x*2=3.9-1.8x*2=2.1x=2.1x2x=4.2
x/2+1.8=3.9x/2=2.1x=4.2
