Question 44717
The are of a rectangle is equal to its length multiplied by its width. We know the length is x, So we can write:
{{{x*width=3x^2+5x}}}
divide both sides by x:
{{{width=3x+5}}}
Thats it!

I hope this helps.
P.S. I am trying to start up my own homework help website. I would be extremely grateful if you would e-mail me some feedback on the help you received to adam.chapman@student.manchester.ac.uk
Adam