Let x0 of type ι be given.
Let x1 of type ι be given.
Let x2 of type ι be given.
Assume H0: x2 ⊆ x1.
Let x3 of type ι be given.
Apply setminusE with
x0,
x1,
x3,
x3 ∈ setminus x0 x2 leaving 2 subgoals.
The subproof is completed by applying H1.
Assume H2: x3 ∈ x0.
Apply setminusI with
x0,
x2,
x3 leaving 2 subgoals.
The subproof is completed by applying H2.
Apply Subq_contra with
x2,
x1,
x3 leaving 2 subgoals.
The subproof is completed by applying H0.
The subproof is completed by applying H3.