Answer:
A cube number is a number multiplied by itself 3 times.
Step-by-step explanation:
A cubed number looks like this: 
The x is whatever number is being cubed.
It is not a function because it does not pass the vertical line test. For every x value there must be only 1 y value but this graph is not a function because there are 2 y values for every y value.
1 ton. = 2000 pounds
2 tons. = 4000 pounds _old model
4000+40=4,040 pounds_newer model