Question 835853
Let a = your age
let b = big brother's age
let c = younger brother's age


I have two brothers. I am eight years older than my younger brother.
a = c + 8
or
c = a - 8
:
 The difference of my age from my younger brother’s age is twice the difference of my age from my big brother’s age.
8 = 2(b - a)
8 = 2b - 2a
2a + 8 = 2b
divide by 2
a + 4 = b
:
 We are now getting old, so the sum of our ages is now 164. How old am I?
a + b + c = 164
replace b with (a+4); replace c with (a-8)
a + (a+4) + (a-8) = 164
3a - 4 = 164
3a = 164 + 4
3a = 168
 a = 168/3 
 a = 56 is his age
:
to check this
56 - 8 = 48 young brothers age
and
56 + 4 = 60 is old brother's age
they add up to:
56 + 60 + 48 = 164