Mixed reality (MR) applications not only require low-latency and high-capacity networks to deliver sensor generated data and virtual holograms, but also demand high-performance computing capability to process data and prepare virtual holograms. Mobile edge computing emerges as a promising networking solution for mixed reality applications. In this demo, we design the MExR system which is a mobile edge resource management platform for mixed reality applications. In this platform, we design and implement the MExR algorithm that manages the traffic load in mobile edge networks and computing workload in edge and cloud servers. We emulate LTE and software-defined network (SDN) in NS-3, manage network performance with the Ryu SDN controller, and design a workload balancing algorithm based on the HAProxy. We develop a real-time MR application using Microsoft hololens and demonstrate the impact of the mobile edge resource management on the MR application. The MExR emulation platform allows the evaluation of various edge networking and computing resource management algorithms for mixed reality applications.