Kendra's age is 13, and according to the problem, Kendra's age is half the age of Justin. We can represent Justin's age as \( a \).
The relationship can be expressed in an equation as follows:
\[ \text{Kendra's age} = \frac{1}{2} \times \text{Justin's age} \]
Substituting in Kendra's age:
\[ 13 = \frac{1}{2} a \]
To eliminate the fraction, we can multiply both sides by 2:
\[ 2 \times 13 = a \] \[ a = 26 \]
Now, looking at the options given in the question, we can rearrange our derived equation \( 13 = \frac{1}{2} a \) to compare with the available choices. If we multiply both sides of this equation by 2, we get:
\[ 2 \times 13 = a \quad \text{or} \quad a = 26 \]
The original form of the equation is:
\[ 2a = 26 \]
None of the provided options match this format. However, from the options:
- \( 2a = 13 \) (this is incorrect)
- \( \frac{1}{2}a = 13 \) (this is actually correct but needs rearranging)
- \( 13a = 2 \) (this is incorrect)
- \( a + \frac{1}{2} = 13 \) (this is incorrect)
So the correct equation that represents Justin's age based on the problem is:
\[ \frac{1}{2}a = 13 \]
Therefore, the answer is:
\(\frac{1}{2}a = 13\) (this one fits).