TMUA 2016 Paper 2 Question 16

In the figure, $PQRS$ is a trapezium with $PQ$ parallel to $SR$. The diagonals of the trapezium meet at $X$. $U$ lies on $SP$ and $T$ lies on $RQ$ such that $UT$ is a line segment through $X$ parallel to $PQ$. The length of $PQ$ is 12 cm and the length of $SR$ is 3 cm. What, in centimetres, is the length of $UT$ ?