Question

Suppose a ⊆ c, and b and c are disjoint. prove that if x ∈ a then x ∈/
b.

Answer 1

If
`x\in A`, then clearly
`x\in C`. We're given that
`B` and
`C` are disjoint, so no element in
`C` is also in
`B`. This means
`x\\ot\in B`.