Question

Does this table represent a function? why or why not? hours of training: 10 20 30 40 50 60 70, monthly pay: 1250 1400 1550 1700 1850 2000 2150
a. no, because each x-value is differet
b. no because none of the y values are the same
c. yes, because the y-values are positive numbers
d. yes, because every x-value corresponds to exactly one y-value 

Answer 1

D. Yes, because every x-value corresponds to exactly one y-value. Just remember for functions: For every x, there is ONE y. :)

Answer 2

d. yes, because every x-value corresponds to exactly one y-value

When considering a function, x-values have to be different, but y-values may all be the same or all different, but what does need to happen is that every x-value needs to correspond to one only y-value - this a consequence of having all x-values different.
Positive or negative values may be part of a function - it will depend on what the variables are to consider or not negative values.