Ответ:

  1. \(19p-19p-y+23y=(-y+23y)=22y\).
  2. \((-16c+3c)+(-21n+13n)=-13c-8n\).
  3. \((1.2s-1.3s)+(2.2t-1.7t)=-0.1s+0.5t\).
  4. \((9-9)+16+u+u=2u+16\).
  5. \((-z+2z)+(28x-28x)+28=z+28\).
  6. \((1.6+1.2-1.7)-v-(1.2f+0.7f)=1.1-v-1.9f\).