Make them both fractions and find a common demoninator. 8 1/13 = 105/13 and 5 1/2 = 11/2. A common denominator is 26, so 105/13 * 2 = 210/26 and 11/2 * 13 = 143/26. You then subtract the fractions to find out how much is left to walk, 210-143 = 67/26, or 2 15/26.
