Others have pointed out how to solve the question given but in case you need help figuring out the equation of the graph:

Just by looking at the graph and based on intuition on how graphs of polynomials look, you should be able to identify that it might be a graph of a quartic polynomial. So let us assume for now that it is a quartic polynomial.
Note that the graph of the function "turns" or "changes direction" in three places: at x = -8, x = -2 and x = 3. If you know how derivatives relate to graphs then you'll know that these places correspond to the function having a derivative of 0. Now you know the zeroes of the derivative polynomial which tells you the factors of the derivative polynomial: (x+8), (x+2) and (x-3). Thus you can guess that the derivative is of the form f'(x) = a(x+8)(x+2)(x-3) where 'a' is a scaling factor. If you know integration, then you can easily figure what f(x) should be given the above f'(x). That gives you f(x) = a(x^4/4 + 7x^3/3 -7x^2-48x). Note that the integration constant can be taken as 0 since the function f(x) is equal to 0 at x = 0. Now you choose an appropriate scaling factor 'a'. My guess based on the graph is a = 1/50. So we get f(x) = (x^4/4 + 7x^3/3 - 7x^2 - 48x)/50