It is linear through a:
Table: the y values have a constant rate of change. For example the y values would be 7, 14, 21, 28 going up by 7 each time. This would not be an example: 6, 12, 17, 18.
Graph: The line of the graph is straight!
Equation: It is in y=mx+b or slope intercept form. Hope this helps!