1)2 1/5 - 1 5/6 = 11/5 - 11/6 =(11*6 - 11 * 5)/30 = 66/30 - 55/30 = 11/30
2)4 29/60 - 11/30 = 269/60 - 11/30 =(269 * 1 - 11 * 2)/60 = 269/60 - 22/60 = 247/60 = 4 7/60
3)71/2 - 4 7/60 = 71/2 - 247/60 = (71 *30 - 247 *1)/60 = 2130/60 - 247/60 = 1883/60 = 31 23/60
4)5 7/15 - 31 23/60 = 82/15 - 1883/60 = (82 * 4 -1883 * 1)/60 = 328 /60 - 1883/60 = - 1555/60 = - 311/12 = - 25 11/12