1. Start with the proportionality relationship: y = kx
2. Substitute the given values y=36 and x=45 to find k: 36 = k \cdot 45
3. Solve for k: k = \frac{36}{45} = \frac{4}{5}
4. Use the found constant k=45 to find y when x=13:
y = \frac{4}{5} \cdot \frac{1}{3}
5. Calculate to find y:
y = \frac{4}{15}
6. Final answer: y=415