PLSS DAU COROANA

Descopera si corecteaza greseala:

a) ∆⊂{ ∆ O ☐ }
b) {x|x ∈ ℕ , x < 4} ⊂ {1,2,3}
c) {x ∈ ℕ |x · 2=6} ⊂ {1,2,3}