Haishan Young Pioneers donated a batch of books (2,800 volumes) to mountain schools. According to the plan, more than one tenth of these books were given to Qingshan Primary School. The rest is given to the Children's Palace, and 136 is given to the Children's Palace, which is three times more than that given to Qingshan Primary School. More than 75% of the remaining 80 books (1520) were given to Xiaomiao Kindergarten, and finally 300 books were left as prizes in the mathematics competition of primary schools in mountainous areas.

x-(3 *(x/ 10+6)+ 136+(x/ 10+6))

= x-(3x/ 10+ 18+ 136+x/ 10+6)

=x-(2x/5+ 160)

=3x/5- 160

= 1520

x=2800