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 <===