Morning everyone,<br/><br/>The original sentence is like this:<br/><br/>There are problems <u>whose</u> solutions have baffled philosophers of all ages.<br/><br/>Using "whose" is a bit informal to me, then I changed it to "of which".<br/><br/>There are problems <u>solutions of which</u> has baffled philosophers of all ages.<br/><br/>Problems is straight connected with solutions, which is a bit strange to me.<br/><br/>However, I cannot insert a comma between them since the relative clause is <u>defining</u>.<br/><br/>Is the "of which" sentence correct?<br/><br/>Thank you.