2x+4=6what is the value of x+2?

You can if the equation is one of a pretty limited set. Many of the types of equations we can actually solve are the ones you study in math classes at various levels. It is not too difficult to find equations that do not have a closed-form solution for the variable.

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The equation for the payment on an amortized loan cannot be solved for the variable representing interest rate, as an example. The interest rate variable is used in the expression in a non-algebraic way. The other variables in that equation are used in an algebraic way, and solutions for those can be found.

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The equation for the payment on an amortized loan cannot be solved for the variable representing interest rate, as an example. The interest rate variable is used in the expression in a non-algebraic way. The other variables in that equation are used in an algebraic way, and solutions for those can be found.