Let total work be 360units(LCM 40,60,12)
Thus efficiencies of A,B,C are 360/90,360/40,12=4,9,30 units respectively or(4+9+30)
=43*8=344 units[Every 3 days 43 units of work is done and 344 is the nearest number to 360 as a multiple of43]
4+9=13 units of work is completed by A and B respectively.
By now 344+13=357 units of work has been done
This at the rate of 30units a day is completed by C in 3/30=
Total work A & B completed is 36+81=117units.
Wages shall also be distributed in the ratio of work done which is 36,81,243