Using the numbers: 0,1,2,4,6,7,8 Make a subtraction problem with the answer of 526.?

Question

Help! It's homework for my 8 year old and we can't even figure it out!!!!

Answer 1

1204-678

The way I came up with this was basic experimentation.
I first tried 1024 - 678 and that was too small, but the last digit was, happily, 6.
So I switched the 0 and the 2.
I have no idea how you'd do this in a methodical but not-too-lengthy manner.

Maybe since you know it has to be a 4-digit number minus a 3-digit number, you could assign letters to numbers and say

(a*1000+b*100+c*10+d) - (e*100+f*10+g) = 526
Then find numbers where d-g is either 6 or -4, etc.
Still seems like a lot of work

Answer 2

tis is the best answer.
1402-876=526