To determine the number of balloons Alexa popped, we can set up the equation based on the information given:
Krista popped 5 balloons and together they popped a total of 13 balloons. Therefore, we can express this as:
\[ n + 5 = 13 \]
where \( n \) represents the number of balloons Alexa popped.
Now, we can solve for \( n \):
\[ n + 5 = 13 \] \[ n = 13 - 5 \] \[ n = 8 \]
So, Alexa popped 8 balloons.
The correct equation is \( n + 5 = 13 \), and the answer is that Alexa popped 8 balloons.