Answer :

MattD
x - age of Mikhail's
3x - age of Gabrielle (three times Mikhail's age)

x + 3x = 56
4x = 56 |:4
x = 14   <-- age Mikhail
3 * x = 14 * 3 = 42   <-- age Gabrielle

As is clear from the job three times the 14 to 42 by adding 14 gives 56, which is behind what they have in total.

G=3M

G+M=56

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3M+M=56

4M=56

M=56/4=14

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G+14=56

G=42

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So Gabriel is 42 and Mikhail is 14.