Is there more to this problem? By saying f(4), you'd be inputting a 4 for every variable x. There is not enough info here to answer the question.
Answer:

Step-by-step explanation:
Given that:
Distance traveled by seal to catch the fish = 15 below sea level
Sea lion wanted to catch a larger fish so sea lion dove 6 feet lesser than two time the distance that the seal traveled.
To find:
The expression to represent the position of the sea lion in the sea.
Solution:
If the distance traveled by seal is represented by
then as per the question statement:
Twice of
= 
6 lesser than twice of
=
- 6
Now, putting the value of
= 15
Therefore, the expression to represent the sea lion's position w.r.to sea level.

<h3>
Answer: True</h3>
Explanation:
Technically you could isolate any variable you wanted, from either equation. However, convention is to pick the variable in which isolating it is easiest, and most efficient.
The key thing to look for is if there's a coefficient of 1. This is found in the second equation for the y term. Think of -4x+y = -13 as -4x+1y = -13. Due to the coefficient of 1, when solving for y we won't involve messy fractions.
If you were to solve for y, then you'd get y = 4x-13, which is then plugged in (aka substituted) into the first equation. That allows you to solve for x. Once you know x, you can determine y.
The Absolute Value of a number is "the magnitude of a real number without regard to its sign". So the Absoulute Value of 1/2 is |1/2|
Answer: f(0) should fit on the graph under 2.5
Step-by-step explanation: