Given the task definition and input, reply with output. This task involves creating answers to complex questions, from a given passage. Answering these questions, typically involve understanding multiple sentences. Make sure that your answer has the same type as the "answer type" mentioned in input. The provided "answer type" can be of any of the following types: "span", "date", "number". A "span" answer is a continuous phrase taken directly from the passage or question. You can directly copy-paste the text from the passage or the question for span type answers. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words. A "number" type answer can include a digit specifying an actual value. For "date" type answers, use DD MM YYYY format e.g. 11 Jan 1992. If full date is not available in the passage you can write partial date such as 1992 or Jan 1992. If you find multiple spans, please add them all as a comma separated list. Please restrict each span to five words.

Passage: In 1718 the Danish claimed the island of St. John to develop sugar plantations and crops such as indigo and cotton; there was especially great demand for sugar and prices were high in Europe. Dutch planters were still important on the island. By mid-1733, planters had developed 109 plantations, and slaveholders owned more than 1,000 African slaves on St. John. One-fifth of the plantations were then devoted to sugar; by the end of the century, most would be, and the total slave population would be 2500. In 1733 the population of African slaves on St. John was more than five times larger than that of the European inhabitants: 1087 slaves and 206 whites. Many of St. John's plantations were owned by people residing on St. Thomas. These absentee landowners hired overseers to manage their lands and slaves on St. John. Under these conditions, overseer cruelty flourished. The Danish West India Company provided only six soldiers for the defense of St. John, which supplemented the local white militia.
Question: How many years was it between when the Danish claimed St. John to when planters had developed 109 plantations?
Answer type: Number
15.