Second voice input starts on second note of triplet
I am copying a piano score in common time. The measure has four triplets for a total of 12 notes. I need to add a second voice where a quarter note is added on the second note of the triplet. This would require a rest of 1/12th to line up with the second note position which mathematically cannot be created from standard rests. While I could I create a triplet consisting of a rest, note, rest such that the only note that is sounded is the second note of the triplet and which gets the note played in the correct location in the measure, the duration is wrong. So how to I create an abnormal rest duration?