Answer:
[tex]4[/tex]
Step-by-step explanation:
Tiana's sister age is [tex]x[/tex].
Tiana's age is:
[tex]\frac{2}{5} x[/tex]
Adding their ages gives [tex]14[/tex].
[tex]x+\frac{2}{5} x=14[/tex]
[tex]1.4x=14[/tex]
[tex]\frac{1.4x}{1.4}=\frac{14}{1.4}[/tex]
[tex]x=10[/tex]
Put [tex]x[/tex] as [tex]10[/tex]:
[tex]\frac{2}{5} (10)=4[/tex]
Therefore, Tiana is 4 years old.