1. **State the problem:** We have 30 g of a 1% w/w hydrocortisone ointment mixed with 12 g of a non-medicated ointment base. We need to find the resulting concentration of hydrocortisone in the mixture. 2. **Formula used:** The concentration in % w/w is given by $$\text{Concentration} = \frac{\text{mass of solute}}{\text{total mass of mixture}} \times 100$$ 3. **Calculate the mass of hydrocortisone:** Since the ointment is 1% w/w, the mass of hydrocortisone in 30 g is $$30 \times \frac{1}{100} = 0.3\text{ g}$$ 4. **Calculate total mass of mixture:** $$30 + 12 = 42\text{ g}$$ 5. **Calculate resulting concentration:** $$\frac{0.3}{42} \times 100 = 0.7142857\% \approx 0.71\%$$ 6. **Interpretation:** The resulting concentration of hydrocortisone in the mixture is approximately 0.71% w/w, which means 0.71 g of hydrocortisone per 100 g of the ointment mixture.