standard_description: Write, read, and evaluate expressions in which letters stand for numbers.
problem_activity: A biologist is tracking the location of three different animals. On the first day of spring, the biologist records the following information about the three animals:
The first animal is located
$$220$$
m below sea level.
The second animal is located at an elevation of
$$0$$
m.
The third animal has an elevation of
$$−10$$
m.
a.   Draw a number line and represent each animal’s elevation on the number line.
b.   Name a possible animal that could be at each elevation.


aligns: no