I think that first one represents a function.
Answer:
The function represents a direct variation
Step-by-step explanation:
we know that
A relationship between two variables, x, and y, represent a direct variation if it can be expressed in the form
or 
In a linear direct variation the line passes through the origin and the constant of proportionality k is equal to the slope m
Let
------> the line passes through the origin

Find the value of k------> substitute the value of x and y
-----> 

Find the value of k------> substitute the value of x and y
-----> 

Find the value of k------> substitute the value of x and y
-----> 

Find the value of k------> substitute the value of x and y
-----> 
The value of k is equal in all the points of the table and the line passes through the origin
therefore
The function represents a direct variation
the equation of the direct variation is equal to

Step-by-step explanation:
Let's say c is the price of cinnamon tea, and s is the price of spice tea.
10c + 2s = 13
16c + 8s = 28
Divide the second equation by 4:
4c + 2s = 7
Subtract from the first equation:
6c = 6
c = 1
Use any equation to find s.
s = 1.5
Therefore, the cinnamon tea costs $1 per pound and the spice tea costs $1.50 per pound.
Answer:
19
Step-by-step explanation:
Given 2 sides of a triangle then the third side x is
difference of 2 sides < x < sum of 2 sides , that is
18 - 2 < x < 18 + 2
16 < x < 20
Then the largest possible length of the third side is 19
The answer is 1. Anything to the 0 power is 1.