The best thing to do is to sit this up into a whole multiple and a remainder. 6 goes into 24, 4 times, but it goes into 30 5 times, therefore, it must 4. You can then divide 2.1 by 6, and this gives you 0.35,
You've then got to add these together equals 4 + 0.35= 4.35
Therefore, 26.1/6= 4.35
Hope this helps :)