Students model contextual situations with systems of two linear equations, defining variables and interpreting coefficients, constants, units, and constraints. They determine whether an ordered pair satisfies both equations and solve systems efficiently by substitution, elimination, or graphing, verifying solutions in the original equations. They identify and interpret one solution, no solution, or infinitely many solutions as intersecting, parallel, or coincident lines, including feasible values and reasonable graph-based approximations in context.