The short piece is **3** feet long

**Step-by-step explanation:**

The given is:

- Mildred cut a 9 foot board into two pieces
- The long piece is twice as long as the short one

We need to find how long is the short piece is

Assume that the length of the short piece is x feet, and the length of long piece is y feet

∵ x represents the length of the short piece

∵ y represents the length of the long piece

∵ The length of the board is 9 foot

∴ **x + y = 9 ⇒ (1)**

∵ The long piece is twice as long as the short one

∴ **y = 2x ⇒ (2)**

Now we have a system of equation to solve it

Substitute y in equation (1) by equation (2)

∵ x + 2x = 9

- Add like terms

∴ 3x = 9

- Divide both sides by 3

∴ **x = 3**

∵ x represents the length of the short piece

∴ The length of the short piece is 3 feet

**The short piece is 3 feet long**

**Learn more:**

You can learn more about the system of equations in brainly.com/question/3965451

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