Question 808041
Let us call the width of the rectangle "w" and the length of the rectangle "l".

The perimeter of the rectangle is the sum of all of its sides, which is the same as saying it is 2*width plus 2*length

We can set up a series of simultaneous equations:

2w+2l=42 ...1
l=2w          ...2

Plugging in the second equation into the first:

2w+2*(2w)=42
2w+4w=42
w=7

Plugging back into the second equation:

l=2*(7)
l=14

Thus, the answer is l=14, w=7.

In these problems, it is always useful to check to make sure the answer makes sense. The problem says that the length of the rectangle rectangle is twice the width. Is it?

7*2=14, so our answer is correct.