well it should be like this tell me if im wrong, ↓
3D + 12
___ ___
3 3
so, hypo thinking once 3 is divided should leave you with . ↓
D = 4 cause once you do all the cancellations it basically leads 2 D then you have to divide →→ 12/3 → 3·4 or 4·3 either way it equals 12 sooo just do the math and you will come up with ...............................↓
-Hope this helped you any if not so comment right answer D=4 :)
