2.3*20+3.5*(x-20)-1.9x=2446+3.5*x-3.5*20-1.9x=2446+3.5x-70-1.9x=24移项3.5x-1.9x=24-46+701.6x=48x=48÷1.6x=30
46+3.5x-70-1.9x=24 3.5x-1.9x=24+70-46 (移相时可将+70放在前面,便于计算) 1.6x=48 x=48÷1.6 x=30