Here's your problem! du is NOT equal to 3, du= 3dx.

And from that it should be easy to see that dx= (1/3)du.

I have no idea what you could mean by "do i divide by 3 to produce 1?". DivideAfter this step i dont know what to do , do i divide by 3 to produce 1?

Please answer in step .Thank youwhatby 3? "Produce 1" where and how? The morepreciseyou are in mathematics, the bettter. Practise being precise.