Question 221768
James is three times as old his oldest son. Five years ago, he was four times as old as his son. What is James present age?


Let James' son's current age be S


Then James' current age is 3S, since he's 3 times his son's age


Five years ago, James would have been: 3S - 5, and his son S - 5


Since 5 years ago, James was 4 times his son's age, then we'll have:


3S - 5 = 4(S - 5)


3S - 5 = 4S - 20


3S - 4 S = - 20 + 5


-S  = - 15


{{{S = (-15)/-1}}} = 15


This means that the son is currently 15 years-old, which makes James {{{highlight_green(45)}}} (3 * 15) years-old.


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Check
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Five years ago, James was 40 (45 - 5)


Five years ago, son was 10 (15 - 5)


Five years ago, James (40) was 4 times his son's (10) age.