graph {
  A -- B [label="12" ]; 
  A -- C [label="5" , color="red"]; 
  A -- D [label="7" , color="red"]; 
  B -- D [label="4" , color="red"]; 
  B -- E [label="7" ]; 
  C -- D [label="9" ]; 
  C -- F [label="7" ]; 
  D -- E [label="3" , color="red"]; 
  D -- F [label="4" ]; 
  E -- F [label="2" , color="red"]; 
  E -- G [label="2" , color="red"]; 
  F -- G [label="5" ]; 
  rankdir=LR;
}