Let x0 of type ι be given.
Let x1 of type ι be given.
Let x2 of type ι be given.
Assume H0: x1 ⊆ x2.
Let x3 of type ι be given.
Apply setminusE with
x0,
x2,
x3,
x3 ∈ setminus x0 x1 leaving 2 subgoals.
The subproof is completed by applying H1.
Assume H2: x3 ∈ x0.
Apply setminusI with
x0,
x1,
x3 leaving 2 subgoals.
The subproof is completed by applying H2.
Assume H4: x3 ∈ x1.
Apply H3.
Apply H0 with
x3.
The subproof is completed by applying H4.