Treat this as an ordinary linear equation. Try to isolate x, as some value. Also remember the basic rules of inequalities: If you're dividing, or multiplying, by a negative, you flip the inequality.
Value of X and Y is 90 and 26 respectively.
G = x
Felicia is Gabriella's age + 6
F = x + 6
Their mother is twice Felicia's age
M = 2(x + 6) or 2x + 12
Tanya is the age of their mother plus Gabriella's age
A = 2x + 12 + x = 3x + 12
3x + 12