Among Spainâs indigenous animals are a wide variety of deer, Iberian wild goats, tortoises, bats, snakes, and small reptiles and amphibians.
Solving Systems of Equations by Substitution Method. Substitution is the most elementary of all the methods of solving systems of equations. Substitution method, as the method indicates, involves substituting something into the equations to make them much simpler to solve.
After completing this tutorial, you should be able to: 1  Solve a system of nonlinear equations in two variables by the substitution method.  Solve a system of nonlinear equations in two variables by the elimination by addition method.