Some university digital libraries provide scanned versions of textbooks and solution manuals for their students.
Websites like Archive.org often host academic texts and solutions. Search for "Das and Mukherjee Integral Calculus Solutions" [1].
The 51st edition of "Integral Calculus" by Das and Mukherjee has several features that make it an excellent resource for students and professionals:
While an authorized 51st edition solution PDF for Integral Calculus