Question

Frank solved an equation and got the result x = x. Sarah solved the same equation and got 12 = 12. Frank says that one of them is incorrect because you cannot get different results for the same equation. What would you say to Frank? If both results are indeed correct, explain how this happened.

Answer 1

Frank is incorrect. 
They could have solved the same equations and got what seems like different answers, however both the answers of x = x, and 12 = 12 mean that the equation has an infinite amount of solutions, or that the answer is all real numbers.

This could have happened because Sarah and Frank may have approached the same equation in different ways, meaning that one simplified or solved the equation with a different, but still correct, strategy.

Hope this helps! :)