Abstract
We investigate sufficient conditions for existence of multiple solutions to a coupled system of fractional-order differential equations with three-point boundary conditions. By coupling the method of upper and lower solutions together with the method of monotone iterative technique, we develop conditions for iterative solutions. Based on these conditions, we study maximal and minimal solutions to the problem under consideration. We also study error estimates and provide an example. Copyright (c) 2016 John Wiley & Sons, Ltd.