Final answer:
The charge qx on x is negative, as indicated by qx < 0. The charge qy on y is positive and has a magnitude greater than the magnitude of qx, inferred from qy - qx > 0.
Step-by-step explanation:
To determine the signs of the charges qy on y and qx on x after specific procedures, we analyze the given information and additional context provided. Since it is stated that qx is less than 0, we deduce that qx must be a negative charge. Furthermore, given that qy - qx is greater than 0 and knowing qx is negative, it can be inferred that qy must be a positive charge with a magnitude greater than the magnitude of qx. This satisfies the condition that the difference between qy and qx is positive, which also aligns with the law of conservation of energy in terms of the redistribution of thermal energy between two objects, as mentioned.