Rubbing sticks together to make math on Mars.

I think Robert Heinlein's Red Planet was the first "grown up" science fiction book I read, in 1982. It was published in 1949, but seemed modern enough to my eleven-year-old self. (With one notable exception, which prompts this post.)
Wikipedia says: "The first Golden Age of Science Fiction -- often recognized as the period from [...]

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I'm reading Han Solo's Revenge, which I first read as a teenager in the 80s. (The book was published in 1979.)
In one scene, at a spaceport on a "highly industrialized, densely inhabited planet," Han has sent Chewie away on a task, but then a potentially dangerous meeting comes up:

His first impulse was to find Chewbacca [...]