To isolate C in the equation X - (S + P - C)E^(RT) + D*E^(RT) = 0, the correct manipulation leads to C = S + P - (X/E^(RT) + D). The discussion highlights the importance of correctly identifying the variables, particularly the different time variables t and T, which affect the calculations. Participants emphasize the need for clarity in the equation's parameters, as well as the significance of the formula in relation to put-call parity in options trading. The conversation also addresses common mistakes, such as sign errors, which can lead to incorrect results. Accurate algebraic manipulation is crucial for determining the correct value of C.