Give the step-by-step reasoning process and then the final answer. There are 12 carpets in house 1, 20 carpets in house 2, and 10 carpets in house 3. If house 4 has twice as many carpets as house 3, how many carpets do all 4 houses have in total?
House 4 has 2 * 10 house 3 carpets = 20 carpets. The total number of carpets across all houses is 12 + 20 + 10 + 20 = 62.
The final answer: 62.