if the following are true:

• a = b
• c = d
• f = a - c

then f = b - d

Start from the conclusion and work back up the proof. Click the arrow to show the parents.

• f = b - d,

  if the following are true:

  • a = b
  • b = c

  then a = c

  • f = a - c
  • a - c = b - d,

    if the following are true:

    • a = b
    • c = d

    then a - c = b - d

    • a = b
    • c = d