If you are looking for the latest editions (including the "Prosveshcheniye" versions), these platforms are the most popular among students:
: Great for mobile users. It’s well-organized by exercise number and often includes multiple solution options for the same problem. gdz po alkgobre avtory iu.n. makarychev
Don't just copy the answers! To actually improve your math skills: Try to solve the problem on your own first. If you are looking for the latest editions
: One of the most comprehensive archives. It usually includes scans of handwritten solutions, which can be easier to follow than typed text. gdz po alkgobre avtory iu.n. makarychev