I Cant Understand What Is The Difference Between..

there is this
question

https://img293.imageshack.us/my.php?image=13985609hu3.gif

which i was told i got the wrong solution because i should make the
minimal function from the whole table
and not from each row
(which by the way i dont know how to build this MUX using this minimal function)

on the other hand there is a question

https://img166.imageshack.us/my.php?image=img8810ev2.jpg

which is solved by my method
which is taking by each row
and not the whole minimal function of the table
and get full point
what is the differense???
why is that??