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