1. The problem is to find the factor pairs of 20. 2. Factor pairs of a number are two numbers that multiply together to give the original number. 3. To find factor pairs of 20, we look for all pairs of integers $a$ and $b$ such that $$a \times b = 20$$ 4. Start with 1: $$1 \times 20 = 20$$ so (1, 20) is a factor pair. 5. Next, try 2: $$2 \times 10 = 20$$ so (2, 10) is a factor pair. 6. Next, try 3: 3 does not divide 20 evenly, so no pair. 7. Next, try 4: $$4 \times 5 = 20$$ so (4, 5) is a factor pair. 8. Next, try 5: already counted in (4, 5). 9. Since 5 is the square root of 20 rounded down, we have found all factor pairs. 10. The factor pairs of 20 are: (1, 20), (2, 10), and (4, 5).