Why can't the number eleven called like onetey one?

just speculating ... we have 20 digits (fingers and toes)

so those numbers have unique names

starting with 20 , the numbers one through nine are just "tacked on"
... twenty-one , twenty-two , etc

same with thirty , forty , fifty , etc

5x + 2y = -4

-5x + 3y = 19

The number eleven is typically pronounced as "e-leven" because this is the standardized way of pronouncing it in the English language. The reason it is not called "onetey one" is because there is a specific naming convention for numbers that follows a pattern.

In English, numbers up to ten have unique names: one, two, three, four, five, six, seven, eight, nine, and ten. After that, the naming convention switches to a combination of the original digits. For example, eleven is a combination of "one" and "ten," and twelve is a combination of "two" and "ten." This pattern continues with thirteen, fourteen, fifteen, and so on, until twenty.

So, the reason we don't say "onetey one" for eleven is simply because it does not follow the established naming convention for numbers in the English language. It's important to note that different languages may have different naming conventions for numbers, so the pronunciation of eleven may vary in other languages.