The submarines depth in the morning is -300m sea level (300 below sea level). During the day the submarine slowly rises by 150m and in the late afternoon it falls again by 50m. Using a number line, determine the final position (depth) in the afternoon.
Starting at -300m,
-300m + 150m = -150m
After rising by 150m, the submarine is at -150m.
-150m - 50m = -200m
After falling by 50m in the late afternoon, the submarine's final position in the afternoon is -200m below sea level.