Originally a rectangle was twice as long as it is wide. When 4m were added to its length and 3m subtracted from its width, the resulting rectangle had an area of 600m^2. How do you find the dimensions of the new rectangle?
The trick with this type of question is to do a quick sketch. That way you can see what is happening and devise a method of solution.
Known: area is
Subtract 600 from both sides
It is not logical for a length to be negative in this context