The working to explain... (x is age)
x = 1/6 * x + 1/12 * x + 1/7 * x + 5 + 1/2 * x + 4
Expand
x= 14/84 * x + 7/84 * x + 12/84 * x + 5 + 42/84 * x + 4
take like
x = 75/84 * x + 9
rearrange
9/84 * x = 9
84yrs.
Son was 42.
Unlucky name for the kid. something harder?
