Gabrielle is x years old.
Felicia is 6 years older.....so Felicia is x + 6
the mom is twice as old as felicia...so the mom is 2(x + 6)
the aunt is x years older then mom....so the aunt (tanya) is 2(x + 6) + x
so Tanya/s age is :
2(x + 6) + x =
2x + 12 + x =
13x + 12 <===