Mark set his watch 12.96 seconds behind, and it falls behind another 1.97 seconds every day. How many days has it been since Mark last set his watch if the watch is 20.84 seconds behind?

The distribution of a sample of the outside diameters of pvc pipes approximates a symmetrical, bell-shaped distribution. the arithmetic mean is 14.0 inches, and the standard deviation is 0.1 inches. about 68% of the outside diameters lie between what two amounts?