Analyze just the right half, assuming the hinge is a spring with stiffness of the left cantilever...find the reaction at the spring, use that to find the moment at the left end. I'll try to post an actual solution after work
Do the right side. Use your standard max displacement equations for a cantilever with a distributed load on it. Then do another max displacement with a point load at the end called P. You won't have "P" so your displacement will be in terms of P. These are delta 1 and delta 2, respectively. Delta 1 + Delta 2 = Delta left beam. Note, Delta 2 is negative. Then you do the left beam the same as Delta 2 in terms of P (max displacement of cantilever with point load). You solve for P... and voila, calculate moment.