conversations.from: human
conversations.value: This math problem has got me stumped: In a certain forest, there are 4 species of trees: oak, pine, spruce, and birch. There is a total of 4000 trees in the forest. Spruces make up 10% of all the trees, and pines 13%. There are as many oaks as spruces and pines put together. How many birches are there in the forest?
  Can you show me the way?
conversations.from: assistant
conversations.value: There are 10/100 * 4000 = 400 spruces in the forest
  There are 13/100 * 4000 = 520 pines in the forest.
  There are as many oaks as pines and spruces together, so there are 400 + 520 = 920 oaks.
  Therefore there are 4000 - 920 - 520 - 400 = 2160 birches.