Question 608740
When Joe was 11 years old, he asked his uncle: how old are you?.
  His uncle answered: I will be 79 when you are my age.
  How old was his uncle when Joe was 11 years old?
:
Let a = Uncle's age when J was 11
:
let y = number of years for this to be true
:
a + y = 79; Uncle + years for this to be true
a - y = 11; Uncle - years is Joe's age
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2a = 90
a = 45 yrs is uncles present age
:
See if that is true
45 - 11 = 34 yrs for this to be true
45 + 34 = 79, uncles age in 34 yrs