Given: △ABC, D and E are points on AB, such that, AD=DE=EB and F and G are points on AC such that, DF∥EG∥BC
Also, M and N are points on BC such that FM∥GM∥AB
Now, DF∥EG∥BC
hence, by basic proportionality theorem
AD:DE:EB=AF:FG:GC
Hence, AF=FG=GC
Similarly, GN∥FM∥AB
Hence, by basic proportionality theorem
AF:FG:GC=BM:MN:NC
hence, BM=MN=NC