It's more like
(A -> B)= C (C is the premise that A implies B)
If not A, then C is not true. (argued for that)
C is true.
Therefore A is true.
Therefore B is true.
(A -> B)= C (C is the premise that A implies B)
If not A, then C is not true. (argued for that)
C is true.
Therefore A is true.
Therefore B is true.