Theorem difss2d

Description: If a class is contained in a difference, it is contained in the minuend. Deduction form of difss2 . (Contributed by David Moews, 1-May-2017)

	Ref	Expression
Hypothesis	difss2d.1	|- ( ph -> A C_ ( B \ C ) )
Assertion	difss2d	|- ( ph -> A C_ B )

Proof

Step	Hyp	Ref	Expression
1		difss2d.1	|- ( ph -> A C_ ( B \ C ) )
2		difss2	|- ( A C_ ( B \ C ) -> A C_ B )
3	1 2	syl	|- ( ph -> A C_ B )