Abstract: In this paper, we study two Hilfer fractional derivatives of the form \begin{equation}D^{\alpha_1, \beta} \left(D^{\alpha_2, \beta} + \lambda \right) x(t) = f(t, x(t)), \ t\in J:=(a,b], \label{ee}\end{equation}\begin{equation}I^{1-\gamma} x(a) = x_a, \gamma = (\alpha_1+\alpha_2)(1-\beta) + \beta,\end{equation} where $\ D^{\alpha_1, \beta}, D^{\alpha_2, \beta}$ is two Hilfer fractional derivatives, $\alpha_1$ and $\alpha_2$ are the order of derivatives,…