We present a new Simplex-based linear arithmetic solver that can be integrated efficiently in the DPLL(
) framework. The new solver improves over existing approaches by enabling fast backtracking, supporting a priori simplification to reduce the problem size, and providing an efficient form of theory propagation. We also present a new and simple approach for solving strict inequalities. Experimental results show substantial performance improvements over existing tools that use other Simplex-based solvers in DPLL(
) decision procedures. The new solver is even competitive with state-of-the-art tools specialized for the difference logic fragment.