You didn’t do what you’re being asked to do.
What is asked:
I have to execute ../gradlew build
What you do
cd ..
gradlew build
That’s not the same thing.
The first one will use the gradlew command found in the .. directory (mdeinum...), and look for the build file to execute in the current directory, which is (for example) chapter1-bookstore.
The second one will execute the gradlew command found in the current directory (mdeinum...), and look for the build file to execute in the current directory, which is mdeinum....
So the build file executed is not the same.