1. **State the problem:** We want to find how many copies can be made for 10 dollars if 30 copies cost 20 dollars. 2. **Identify the ratio:** The ratio of copies to dollars is given as 30 copies for 20 dollars. 3. **Set up the proportion:** Let $x$ be the number of copies for 10 dollars. The proportion is $$\frac{30}{20} = \frac{x}{10}$$ 4. **Solve the proportion:** Cross-multiply to get $$30 \times 10 = 20 \times x$$ which simplifies to $$300 = 20x$$ 5. **Isolate $x$:** Divide both sides by 20 to find $$x = \frac{300}{20} = 15$$ 6. **Interpretation:** For 10 dollars, you can make 15 copies at the same rate. **Final answer:** $$\boxed{15}$$ copies can be made for 10 dollars.