Blood flow problem using the continuity equation

Blood flow increases during exercise by the dilation of blood vessel diameter together with an increase in
blood pressure. Suppose that the flow rate increases by a factor of 4.5 and blood pressure increase by
40%. Calculate the factor by which the average blood vessel diameter must have increased to produce this
flow. Assume that blood is a Newtonian fluid.

In this question, I tried to solve it by the continuity equation but it did not work. We took in the class only the continuity equation but I noticed that it can be solved by an equation called: Hagen–Poiseuille equation.

I don’t know what that is but can anyone help me solving this problem? and can you please tell me a strategy to solve any smiliar kind of problems when I face tomorow (I have final exam tomorrow) xDDD