A school buys $$720 $$ books for Grades 4, 5 and 6. The number of books in Grade 5 is $$4$$ more than twice of that in Grade 4, and the number of books in Grade 6 is $$8 $$ more than $$3$$ times that in Grade 4. How many books does Grade 6 get? 
Overseas Competition->Knowledge Point->Word Problem Modules->Questions Involving Sum, Difference and Multiples->Problems of Sum and Multiple