C and D is 1 more than A and B while having the lowest number, which also means it has the highest number. I started with giving C 9 and subtracting 4 and giving D 5, then I chose 2 numbers between 9 and 5 for A and B. If I gave B 8, then A would have to be 5, but D is already the lowest number so I gave B 7 and A 5 which works out with the requirements. I guess I got lucky when choosing 9 for C, but if 9 didn't work, then I'd go down to 8. I suspected 9 would work because B had to be 7 or 8 while not being the highest number and being less then C and D while being added to A. Make sure to leave feedback!
