1. **State the problem:** We know that 26 dogs were adopted this spring, which is 130% of the number adopted last spring. We need to find how many dogs were adopted last spring. 2. **Formula and explanation:** If $x$ is the number of dogs adopted last spring, then 130% of $x$ equals 26. We write this as: $$1.30 \times x = 26$$ 3. **Solve for $x$:** $$x = \frac{26}{1.30}$$ 4. **Simplify the fraction:** $$x = \frac{26}{\cancel{1.30}} \times \frac{\cancel{1}}{1} = 20$$ 5. **Interpretation:** Last spring, 20 dogs were adopted. 6. **Number line illustration:** - Mark 0 at the start. - Mark 20 to represent last spring's adoptions. - Mark 26 to represent this spring's adoptions, which is 130% of 20. This shows the increase from 20 to 26 dogs adopted.