17-2x+1=5-2x = 5 - 18-2x = -13x = 13/21/2=3x-13x = 1/2 + 13x = 3/2x = 1/24x-3（20-x）=34x - 60 + 3x = 37x = 3 + 607x = 63x = 96x+4/3=4x+5/46x - 4x = 5/4 - 4/32x = -1/12x = -1/24是对的么？已验算，对的