A dime is a ten cent coin while a quarter is a 25 cent coin. The total of the money should be $8.40. Let x be the number of dime and y be the number of quarter. The equation that would best represent the given problem is,
0.1x + 0.25y = 8.40
x + y = 45
The values of x and y are 19 and 26, respectively. Thus, there are 19 dimes and 26 quarters.
So, for something to be a function see that we want one x value to correspond to only one y value. Solving for y here gives us:

So we see that for every x, there are actually two y values output, so it is not a function.
Answer:
y = 8x + (any number other than 7)
Step-by-step explanation:
All of the other lines will be parallel to y = 8x + 7 they will never cross so there isn't a solution.