Answer:
f = 7.5h
Explanation:
The graph is a straight line through the origin, so represents a proportional relation. For some value of k, you have ...
f = k×h
The constant of proportionality can be found from any of the points on the graph. I generally find it convenient to use points where the line crosses a grid intersection. (h, f) = (2, 15) is one such point.
k = f/h = 15/2 = 7.5
Your equation is ...
f = 7.5h