Question 1143697
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Subtract 4 from his age 4 years from now (a) to get his current age.  (How do you write "4 less than a"?)<br>
Then subtract 8 from his current age to get is age 8 years ago.  (How do you write -- and simplify -- "8 less than 4 less than a"?)<br>
Of course, with a little experience with this kind of problem, you can simply subtract 12 from his age 4 years from now to get his age 8 years ago, since there is a difference of 12 years between "4 years from now" and "8 years ago".