2. Between Xia and Zhou Dynasties (using a mathematical noun): Shang.

3. Abacus ball (A mathematical term): algebra

4. Don't cheat in the exam (use a math noun): True score

Analyze it:

Goodbye, mom (type a math noun). Bye, bye, mom. The first answer of mom's combination is the denominator.

Between Xia and Zhou Dynasties, between Xia and Zhou Dynasties was Shang Dynasty, a mysterious business.

Abacus ball, instead of or on behalf of numbers, answers algebra.

Not cheating in the exam means that the score is true and the answer is true.

Extended data:

Guessing is an intellectual game with a long history, which originated from the Eight Diagrams of the Book of Changes in China. Guessing refers to guessing something or words within a specified range and according to certain rules through given suggestive words or images. In the form of solve riddles on the lanterns, China riddles are the most common, and the characteristics of Chinese characters and language are often used consciously to solve riddles.

References:

Baidu encyclopedia: riddle