Ava's Age Calculation

Emily is twice as old as her sister Ava. If the sum of their ages is 30 years, how old is Ava?

Let Emily's age be represented as $E$ and Ava's age as $A$. Thus, we can establish the following equations:

1) $E = 2A$

2) $E + A = 30$

Using these equations, solve for Ava's age.