if the following are true:

• x = 12
• d = x + 13

then d = 25

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

• d = 25,

  if the following are true:

  • a = b
  • b = c

  then a = c

  • 12 + 13 = 25, 12 + 13 = 25
  • d = 12 + 13,

    if the following are true:

    • a = b + c
    • b = d

    then a = d + c

    • x = 12
    • d = x + 13