Wave erosion causes a certain coastline to recede at a rate of 3 centimeters each year. This occurs uninterruped for a period of 8 years

The expression 8 (-3) represents the recession of the coastline after 8 years if the coastline recedes 3 centimeters each year. 8 (-3) = - 24. So, the coastline's new position is 24 centimeters farther inland than it was 8 years ago.

answer = 24