A dog weighs 20% more than it did three months ago. It weighs 36 pounds now. How much did the dog weigh three months.

1. Identify the current weight of the dog: 36 pounds.

2. Determine the percentage increase in weight: 20% or 0.2.

3. Use the formula for the original weight:
\text{Original Weight} = \frac{36}{1 + 0.2}

4. Calculate the denominator:
1 + 0.2 = 1.2

5. Calculate the original weight:
\text{Original Weight} = \frac{36}{1.2}

6. Perform the division:
\text{Original Weight} = 30

Therefore, the dog weighed 30 pounds three months ago.