Solve the inequality: |2x + 1| > 3

19. Solve the inequality: $|2x + 1| > 3$

✅ Correct.
The steps taken to solve the absolute value inequality are correct, leading to the solution $x > 1$ or $x < -2$.

20. If $A \subseteq B$ and $B \subseteq A$, then:

❌ Incorrect (notation error in explanation, but final answer is correct).
The definition of a subset is $A \subseteq B$, not $A \in B$. The statement "$A \in B$ means that every element in set A is also an element in set B" is incorrect notationally. It should be "$A \subseteq B$ means that every element in set A is also an element in set B." However, the conceptual understanding that if $A \subseteq B$ and $B \subseteq A$, then $A = B$ is correct.