Let total work to be done = L.C.M.(8,10,12) = 120 units Let efficiency of Rohan, Mohit and Vikas be x,y,z respectively. Rohan and Mohit together can build the wall in 8 days,⇒ x+y=
120
8
=15 units/day ----------(i) Similarly, y+z=
120
10
=12 units/day ----------(ii) and z+x−
120
12
=10 units/day ----------(iii) Adding equations (i), (ii) and (ii), we get : ⇒ 2(x+y+z)=15+12+10=37 ⇒ x+y+z=