Triangle ABC being similar to triangle LMN by the AA similarlity postulate means that m<A = m<L; m<B = m<M; m<C = m<N. Let m<M = x, then 81 + x + 2x = 180; 3x = 180 - 81 = 99. x = 99 / 3 = 33. Therefore, m<M = 33 degrees.Hope this helps. Let me know if you need additional help!