Niki has $15$ dollars more than twice as much money as her sister Amy. If Niki gives Amy $30$ dollars, then Niki will have hals as much money as her sister. How many dollars does Niki have?
1. Let \( N \) be the amount of money Niki has.
2. Let \( A \) be the amount of money Amy has.
3. According to the problem, Niki has $15$ dollars more than twice as much money as her sister Amy. This can be written as:
   \[
   N = 2A + 15
   \]
4. If Niki gives Amy $30$ dollars, then Niki will have half as much money as her sister. This can be written as:
   \[
   N - 30 = \frac{A + 30}{2}
   \]
5. Substitute the expression for \( N \) from the first equation into the second equation:
   \[
   2A + 15 - 30 = \frac{A + 30}{2}
   \]
6. Simplify the left-hand side:
   \[
   2A - 15 = \frac{A + 30}{2}
   \]
7. To eliminate the fraction, multiply both sides by 2:
   \[
   2(2A - 15) = A + 30
   \]
   \[
   4A - 30 = A + 30
   \]
8. Subtract \( A \) from both sides to isolate terms involving \( A \):
   \[
   4A - A - 30 = 30
   \]
   \[
   3A - 30 = 30
   \]
9. Add 30 to both sides to solve for \( A \):
   \[
   3A = 60
   \]
   \[
   A = 20
   \]
10. Substitute \( A = 20 \) back into the first equation to find \( N \):
    \[
    N = 2(20) + 15
    \]
    \[
    N = 40 + 15
    \]
    \[
    N = 55
    \]

The final answer is \(\boxed{55}\).