书架上层有15本书，下层有19本，妈妈让你把上、下层的书摆的一样多，你要从下层拿几本放到上层呢？+a+K6P0|)O;H1B3Z/D7N)F*}'n2v
算式：提示1L6w.@+u5x'e9q6U3P1x;i9x+a+K6P0|)O;H1B3Z/D7N)F*}'n2v
算式：提示1{;k:L+f0].P+a+K6P0|)O;H1B3Z/D7N)F*}'n2v
答：你要从下层拿0V6x;d0r本放到上层。+a+K6P0|)O;H1B3Z/D7N)F*}'n2v