SOLUTION: In the year 2000 Donald was 12 and his father was 40. In which year was Donald's father 8 times as old as Donald?

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Question 394149: In the year 2000 Donald was 12 and his father was 40.
In which year was Donald's father 8 times as old as Donald?
Answer by Edwin McCravy(20056) About Me  (Show Source):
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In the year 2000 Donald was 12 and his father was 40.
In which year was Donald's father 8 times as old as Donald?


Let the desired year be x years before 2000 or the year 2000-x.

x years before 2000 Donald was 12-x and his father was 40-x.

So we want 12-x to be 1%2F8th of 40-x.  To say that in algebra,

          12 - x = 1%2F8(40 - x)

Clear of fractions by multiplying both siades by 8

         96 - 8x = 8*1%2F8(40 - x)

Cancel the 8 and the 1%2F8 and you have

         96 - 8x = 40 - x
             -7x = -56
               x = 8

So the year was 2000-x or 2000-8 or 1992, when Donald was 4 and his
father was 32.

Edwin