The length of the missing sides

length-14cm width-7cm

Step-by-step explanation:

To work out the sides, you can use 2l+2w=42. Since the length is twice the width, this becomes 2(2w)+2w=42.

This can be expanded to 4w+2w=42 or 6w=42.

From there, we can divide both sides by 6 to isolate w, meaning w=7.

Since the length is twice the width, it is given by l=2×7 or l=14.

**This question involves writing and solving algebraic equations from worded questions, which you may wish to revise. I'm always happy to help!

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