A system of equations is a set of two or more equations involving the same variables. The solutions to a system are values for these variables that satisfy all the equations simultaneously. The most common systems are systems of linear equations, which contain only linear equations. A system of equations is usually written as a vertical list with a curly bracket on the left-hand side. Graphically, solutions to systems of equations are the points where the graphs of the equations intersect. For this reason, these solutions are usually expressed as coordinates. Since the graphs of linear equations are lines, they can have $0,$ $1,$ or infinitely many points of intersection. Therefore, the number of solutions for a linear system is also $0,$ $1,$ or infinitely many solutions. Systems can contain many different types of equations. Systems of equations can be solved graphically or algebraically.