Two steps to this problem. First find the fertilizer required per square meter, then multiply by the amount of square meters. 150/6 is the amount per square meter, which simplifies to 25 grams of fertilizer per square meter. 25x13 is the total fertilizer required for 13 square meters, which simplifies to 325 grams of fertilizer, which is the solution.
Therefore the solution is 325 grams of fertilizer.
