Question 984022
he has 5x dollars to 6x dollars.  or (5/6) x to x, if you wish.  I will remove the fraction.

5x-800 is to 6x as 1:2

Cross-multiply
6x=2(5x-800)
6x=10x-1600
-4x=-1600
x=$400

So Bill started with $2000 (the answer) and Henry with $2400.
After spending $800, Bill had $1200, which is half of $2400.