Question 1092775
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S = D + 6.           ("Sally is 6 years older than Donald")

(D + 6) + D = 18     ("The 2 children have a total age of 18 years")


=========================>  2D + 6 = 18  ====>  2D = 18-6 = 12  ====>  D = {{{12/2}}} = 6.


<U>Answer</U>.  Donald is 6 years old, Sally is 12.
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