options: Apply and extend previous understandings of addition and subtraction to add and subtract rational numbers; represent addition and subtraction on a horizontal or vertical number line diagram.

Apply and extend previous understandings of multiplication and division and of fractions to multiply and divide rational numbers.

Solve real-world and mathematical problems involving the four operations with rational numbers. (Computations with rational numbers extend the rules for manipulating fractions to complex fractions.)
problem_activity: A red-throated loon is a type of diving bird that dives for its food. One particular loon dives for 8 seconds to a depth of 12 feet under the surface of the water.
a.   Assume the loon dives at a constant rate. Write an equation that can be used to represent the elevation,
$$y$$
, of the loon after
$$x$$
seconds into the dive.
b.   If the loon is at a depth of 22.5 feet under the surface of the water, how long was it diving for?


correct_option_index: 1