The textbook itself is sometimes available for reference in digital formats on the Internet Archive Study Tips for Quantum Mechanics
A breakdown of the in the 4th edition?
If solutions are unavailable, consider these study strategies:
Problems in Liboff are layered. For example, a typical problem might ask the student to derive the transmission coefficient for a step potential, then extend it to a barrier, and finally discuss the classical limit. Another might request the construction of raising and lowering operators for the harmonic oscillator without prior introduction. This design is intentional: the struggle is the learning. However, without feedback, this struggle can become paralysis. Hence the allure of the solutions manual.