In a scenario where scientists decipher a Math book of an alien culture, the last thing to expect is equations presented the way we know them.The way we write mathematical equations, is mostly taken for granted, as we know of one source. Early developments by the Arabs started with Algebra. The Renaissance in Europe was another hallmark in the evolution of equations, as new calculation methods were developed by Leibnitz, Newton, Euler, and so on until today.
In a parallel "world", the Chinese, Mayans, Aztecs and Incas have developed some type of technology, which may have required some advanced mathematics beyond arithmetic. They may have (or have not) developed some mathematical equations, which may have been written using different symbols, but not only that. All those equations may have their own writing system, as long as they were developed before first contact with the Europeans.
To clarify my point, take a look at the formula editor in this article. The editor converts a string of ASC-][ characters from a keyboard, and converts it into a visual representation which is easier to read than the string of ASC-][ characters. This representation is called a typeset representation and an example is shown at the upper-right of the article page.
The string of characters is rather limited in the number of ways we can represent a single equation, and it does not matter what symbols different cultures used for each mathematical operation. That is not the point. The point is how different cultures write their version of typeset representation before the computer era? It may be an outdated representation from an old Earth culture, or alien origin. Whatever it is, it must have been independently developed and without the influence of European contact.