What is the formula for do and does?

Could you please clarify the context in which you're asking about the "formula for do and does"? In English grammar, "do" and "does" are verbs that are often used as auxiliary verbs to form questions, negatives, and emphatic statements. They don't have a mathematical formula like in algebra or physics. Instead, their usage depends on the subject of the sentence and whether it's singular or plural. For example, "I do my homework" is present tense with a singular subject, while "They do their homework" is present tense with a plural subject. And for questions, you'd use "Do you..." for singular or plural subjects in the second person, and "Does he/she/it..." for singular subjects in the third person. Is there a specific aspect of their usage you're trying to understand?