How can antherosclerosis and a blood clot result in death.

Well: Different ways. In atherosclerosis a piece of the hard wall of an artery can break off and block a prominent place in the brain causing a massive stroke resulting in death. A blood clot usually travels through the venous system through the heart landing in the lungs causing a pulmonary embolus or infarct (resulting in cell death). If the damage to the lung is massive enough you can die.