Understand that the graph of an equation in two variables is the set of all its solutions plotted in a coordinate plane.
Explain why the x-coordinates of the points where two graphs intersect are the solutions; find solutions using technology and a table of values.
Write a function that describes a relationship between two quantities.
Interpret parameters for linear functions in terms of the situation they model.
Prove that when a given system is in two variables, replacing one equation with the sum of that equation and a multiple of the other results in the same solution.
Solve a system of linear equations exactly and approximately focusing on two variables.