Example of sets A, B, C, for A ∈ B, B ∈ C, but B should not contain A.

2-digit numbers less than 91 which are 1 less than a multiple of 10

Ateacher wanted to buy a chair, a bookshelf, two tables and a desk. she spent $900 for all five items and the chair and the desk combined 70% of her total. if the bookshelf cost $50, how much did each of the tables cost?

Alex's monthly take home pay is $2,500. what is the maximum bad debt payment he can maintain without being in credit overload?