Set theory and algebra can be used to make money in various fields. Here are a few examples:

1. Data analysis: Set theory and algebra are used in data analysis to analyze and manipulate large datasets. For instance, set theory can be used to identify commonalities between different sets of data, while algebra can be used to transform and manipulate data.

2. Cryptography: Set theory and algebra are used in the development of cryptography algorithms that make it difficult for unauthorized individuals to access sensitive information. Cryptography is used by businesses to protect their financial information, customer data, and other confidential information.

3. Finance: Set theory and algebra are used in financial modeling and portfolio management. In portfolio management, algebra is used to calculate the optimal allocation of investments in a portfolio, while set theory can be used to identify correlations between different investments.

4. Machine learning: Set theory and algebra are used in machine learning algorithms that can identify patterns and make predictions based on large datasets. Companies that use machine learning to improve their products or services can gain a competitive advantage and increase revenue.

5. Optimization: Set theory and algebra are used in optimization algorithms that can be used to optimize production processes, supply chain management, and other business operations. By optimizing these processes, companies can increase efficiency and profitability.

These are just a few examples of how set theory and algebra can be used to earn money. The key is to identify the specific application and use the appropriate mathematical tools to solve the problem at hand.