1. **State the problem:** We have 80 cm³ of liquid A with density 1.8 g/cm³ and 40 cm³ of liquid B with density 1.2 g/cm³ mixed to form 120 cm³ of liquid C. We need to find the density of liquid C. 2. **Formula used:** Density $\rho = \frac{\text{mass}}{\text{volume}}$. 3. **Calculate mass of liquid A:** $$m_A = \rho_A \times V_A = 1.8 \times 80 = 144 \text{ g}$$ 4. **Calculate mass of liquid B:** $$m_B = \rho_B \times V_B = 1.2 \times 40 = 48 \text{ g}$$ 5. **Calculate total mass of liquid C:** $$m_C = m_A + m_B = 144 + 48 = 192 \text{ g}$$ 6. **Calculate density of liquid C:** $$\rho_C = \frac{m_C}{V_C} = \frac{192}{120}$$ 7. **Simplify the fraction:** $$\rho_C = \frac{\cancel{192}}{\cancel{120}} = \frac{16}{10} = 1.6 \text{ g/cm}^3$$ **Final answer:** The density of liquid C is $1.6$ g/cm³.