Ответ:

  1. \((x-1)+(12-7.5x)=x-1+12-7.5x=11-6.5x\).
  2. \((2p+1.9)-(7-p)=2p+1.9-7+p=3p-5.1\).
  3. \((3-0.4a)-(10-0.8a)=3-0.4a-10+0.8a=0.4a-7\).
  4. \(b-(4-2b)+(3b-1)=b-4+2b+3b-1=6b-5\).
  5. \(y-(y+4)+(y-4)=y-y-4+y-4=y-8\).
  6. \(4x-(1-2x)+(2x-7)=4x-1+2x+2x-7=8x-8\).

Ответ: а) \(11-6.5x\); б) \(3p-5.1\); в) \(0.4a-7\); г) \(6b-5\); д) \(y-8\); е) \(8x-8\).