If the farmer sells an average of 16 3/4 bushels each day, then after 6 days the farmer would have sold
16 3/4 * 6
We can rewrite the mixed number 16 3/4 as an improper fraction for easier multiplication
16 3/4 = 67/4, so
16 3/4 * 6 = 67/4 * 6
67/4 * 6 = 67/4 * 6/1 = 402/4 = 100 2/4 = 100 1/2 bushels sold after 6 days
If the farmer began with 180 bushels, then after 6 days the farmer has
180 - 100 1/2 = 79 1/2 bushels