We have now seen how to solve for two simultaneous linear equations in their most general form. These forms were also convenient, because one equation contained the variable x in isolation while the other equation gave us y explicitly in terms of x. If we don't already find the two equations in these convenient forms, we will need to apply the rules of algebra to give them to us this way before we perform the substitutions. Let us return to the forms ax + by = c that we saw earlier. On the following page, you will be able to choose integer constants for a, b, and c for two separate equations and see their graphs. You have already learned that with the rules of addition and subtraction, we may transform equations to equivalent forms without changing their solutions. We may also apply the rules of multiplication and division similarly. We found that with these four rules we can rearrange the equations so that each one isolates one of the variables. From there, we can apply substitution to solve for the value of each variable.