Multiply 391 by 2.

Brief Explanation:

Step-by-step Solution:

1. Step 1: Multiply the ones digit (1) by 2: $$1 \times 2 = 2$$. Write down 2.
2. Step 2: Multiply the tens digit (9) by 2: $$9 \times 2 = 18$$. Write down 8 and carry over 1.
3. Step 3: Multiply the hundreds digit (3) by 2: $$3 \times 2 = 6$$. Add the carried-over 1: $$6 + 1 = 7$$. Write down 7.

Answer: 782