Question 246834
http://en.wikipedia.org/wiki/Diophantus
d/6+d/12+d/7+5+d/2+4=d 
multiply both sides by  84(7*12)lcd

14d+7d+12d+5*84+42d+4*84=84d
combine
75d+9*84=84d
subtract 75d from both sides

9*84=9d
divide by 9
84=d