Hydrogen is the only element where the isotopes are given specific names. Common hydrogen, which has zero neutrons, is called protium. Hydrogen with one neutron is called deuterium and hydrogen with two neutrons is called tritium. See the picture at the top of the page.
The following steps can be used as a guide as you read through the examples for using the substitution method. Steps for Using the Substitution Method in order to Solve Systems of Equations. 1  Solve 1 equation for 1 variable. ( 2 Put in y = or x = form). 3  Substitute this expression into the other equation and solve for the missing variable. 4  Substitute your answer into the first equation and solve.
In general, the method of solution for general systems of equations is to solve one of the equations (you choose which) for one of the variables (again, you choose which). Then you plug the resulting expression into the other equation for the chosen variable, and solve for the values of the other variable.