1. **State the problem:** We want to find how many gallons of yellow paint are needed to make 48 gallons of green paint, given that the mixture ratio is 5 gallons of blue paint to 3 gallons of yellow paint. 2. **Understand the ratio:** The ratio of blue to yellow paint is $5:3$. This means for every 5 gallons of blue, 3 gallons of yellow are used. 3. **Calculate total parts in the ratio:** Total parts = $5 + 3 = 8$ parts. 4. **Find the amount of one part:** Since the total mixture is 48 gallons, one part equals $$\frac{48}{8} = 6$$ gallons. 5. **Calculate gallons of yellow paint:** Yellow paint is 3 parts, so $$3 \times 6 = 18$$ gallons. **Final answer:** To make 48 gallons of green paint, you need 18 gallons of yellow paint.