I request a clarification/disambiguation: is e.g. ghj equal to (g*100)+(h*10)+(j) or equal to (g*h*j)?
The former makes the most sense, but my mind went first to the latter.
For the purposes of this puzzle, you have found four.
Each combination actually can be counted as two. Just invert b/a=d/c=
@drbitboy, I like brute force but why did you ignore b/a?
Also, once a/b are selected that narrows down the choice for c/d you can continue of a/b!=c/d. There is no point wasting time on the third fraction.
de is calculated twice. First as a decimal number, then as a hex number. Why multiply by 16.