Simultaneous equations are two or more equations with the same unknown variables. There are two main methods to solve simultaneous equations: 1) Using graphs - make a table of values, plot the equations on a graph, and find where the graphs intersect. 2) Using algebra - organize the equations, make coefficients equal, eliminate a variable, solve the resulting equation, substitute values back into the original equations, and check the answer. The algebraic method follows the steps of NO MESS: Organize, Make equal, Eliminate, Solve, Substitute.