my age plus my son age is equal to my fathers age which is 78 years old.
Let My age = M
Let my son's age = S. So
M + S = 78
when I was my son age
Let that be x years ago, which means
M - x = S and my son was S - x
he was just a quarter as old as i am now.
S - x = M
So we have three equations in 3 unknowns:
M + S = 78
M - x = S
S - x = M
Clear the fraction in the third one:
M + S = 78
M - x = S
4S - 4x = M
Line up the letters and symbols:
M + S = 78
M - S - x = 0
-M - 4S - 4x = 0
Solve that system of equations and get
M = 48, S = 30, x = 18
how old am i?
So I am 48.
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Checking:
my age plus my son age is equal to my father's age which is 78 years old.
48+30 = 78 that checks
when I was my son age,
that is 18 years ago when I was 48-18 or 30. That checks.
he was just a quarter as old as i am now.
18 years ago he was 30-18 or 12, which is just a quarter of 48.
That checks.
Edwin