I want to know the meaning of the following word.  meaning Thanks.

One Arabian scholar has written wrote,_"The rich say that earning money is the toughest task in the world. .But However, the wise would say, "No. Acquiring knowledge is the hardest job."__Now the question is who are is right, ,the rich or the wise one? ?

Does "Toughest" means the most difficult? (i don,t know)

Yes. You guessed correctly.

Both are right.  It is like asking a question to a bird and a fish.  Which is the toughest? To fly or to swim?