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! :)
