Simply having the final number (the answer) is often useless in Calculus and Logarithms because there are multiple ways to get to a number, but only one correct mathematical logic. Many students seek the rather than just the Answer Book, as it shows the step-by-step work.
If you have legitimate access to the Kumon Level L solutions, or if you are using the graded sheets to review your work, here is the most effective way to utilize them: kumon l answer book