1. **State the problem:** We have two similar triangles, CDE and FGH. We know sides CD = 6, CE = 10.8 in triangle CDE, and side GH = 18 in triangle FGH. We need to find side HF. 2. **Recall the property of similar triangles:** Corresponding sides of similar triangles are proportional. This means: $$\frac{CD}{GH} = \frac{CE}{HF}$$ 3. **Identify corresponding sides:** Since CD corresponds to GH, and CE corresponds to HF, we set up the proportion: $$\frac{6}{18} = \frac{10.8}{HF}$$ 4. **Solve for HF:** Cross-multiply: $$6 \times HF = 18 \times 10.8$$ $$6HF = 194.4$$ Divide both sides by 6: $$HF = \frac{194.4}{6} = 32.4$$ 5. **Conclusion:** The length of side HF is $32.4$ units.