Let us say that the number of pens that Matt has is x.
Therefore the number of pen that Sarah has is:
Sarah pens = (5/4) (1/3) x = (5/12) x
So the total number of pens they have is:
total = x + (5/12) x = (17/12) x
Hence the fraction of Matts pen is:
fraction = x / [(17/12) x]
fraction = 12/17
