1988 AMC 12 Question 25

$X,$ $Y,$ and $Z$ are pairwise disjoint sets of people. The average ages of people in the sets $X,$ $Y,$ $Z,$ $X\cup Y,$ $X\cup Z,$ and $Y\cup Z$ are given in the table below. Set $X$ $Y$ $Z$ $X\cup Y$ $X\cup Z$ $Y\cup Z$ Average age of
people in the set $37$ $23$ $41$ $29$ $39.5$ $33$ Find the average age of the people in the set $X\cup Y\cup Z.$