Answer:
Gabrielle is 34; Mikhail is 17
Step-by-step explanation:
Lets use G for Gabrielle and M for Mikhail
G=2M since Gabrielle is twice as old as Mikhail
G+M=51 since their ages add up to 51
We can do M=51-G and replace M is G=2M with that equation
G=2(51-G)
G=102-2G
3G=102
G=34
Then plug that in to M=51-G
M=51-34
M=17
Hope this helps
