A (debtor) is indebted to B (creditor) PhP300,000.00. X, a third party, offered to give B the PhP300,000.00, to which B agreed. B, however failed to disclose that there was a prior partial payment made by A in the amount of PhP100,000.00. X paid B the entire amount of PhP300,000.00

Question:

What is the effect of the payment made by X in so far as the obligation of A to B is concerned?

Can X proceed against A and demand payment from the latter? If yes, how much can X collect from A?

S (debtor) is indebted to T (creditor) in the amount of PhP50,000.00. S proposed to T that Y will be the one to pay the debt, making him (Y) as the new debtor. T agreed to the proposal. It turned out, however, that Y is insolvent so T was not able to collect the amount due from Y.

Question:

Can T enforce the obligation to S, given the insolvency of Y?