I need help setting up this problem:
A rectangle is twice as long as it is wide. If its length and width are both decreased by 4cm, its area is decreased by 164cm2. Find its original dimensions.

Hello cacia. First thing is to decide what to call the unknows - let's call them L (for length) and W (width). You know that the rectangle is twice as long as it wide, so:

L = 2W

Since the area of a rectangle is L*W, you know from the second sentence in the problem that:

(L-4)*(W-4) = L*W-164.

You should now be able to solve these two equations to find values for L and W.