Question 287779
Mr. Parabol, a mathematics teacher was traveling by bus with his family consisting of his mother,wife,son,and daughter. The bus conductor doubting the
 son's right to have a half-fare ticket asked, How old is your daughter? 
Mr.Parabola, irritated at having his honesty questioned,confused the conductor with his answer:
 my daughter is twice as old as my son. My wife is three times as old as the
 sum of the ages of my son and daughter, and iam as old as my wife and daughter.
 My mother whose age is the total of all our ages is now 69.
 can you help the conductor in finding the age of the girl?
:
"my daughter is twice as old as my son."
d = 2s
:
"My wife is three times as old as the sum of the ages of my son and daughter,"
w = 3(s+d)
w = 3s + 3d
Replace d with 2s
w = 3s + 3(2s)
w = 3s + 6s
w = 9s
:
"I (p) am as old as my wife and daughter."
P = w + d
Replace d with 2s
p = w + 2s
Replace w with 9s
p = 9s + 2s
p = 11s
:
"My mother whose age is the total of all our ages is now 69."
 p + w + d + s = 69
Replace p, w, d, from the above equations
11s + 9s + 2s + s = 69
23s = 69
s = {{{69/23}}}
s = 3 yrs old is the son
then
2(3) = 6 yrs old is the daughter
:
can you help the conductor in finding the age of the girl?
:
Check solution
11(3) + 9(3) + 2(3) + 3 = 
33 + 27 + 6 + 3 = 69