Подобные слагаемые: -2,5a+1,8a+1,5a; 3,2b-4,3b-3,2b; 1/2c+1/3c+1/6c; 1,9d-4,2d+3,1d; 7,2a-5a-1,3a; 1/3b+1/5b-2/15b.

-2,5a+1,8a+1,5a=-2,5a+2,3a=0,2a
3,2b-4,3b-3,2b=-4,3b-0b=-4,3b
1/2c+1/3c+1/6c=3/6c+2/6c+1/6c=6/6c=1c
1,9d-4,2d+3,1d=5d-4,2d=0,8d
7,2a-5a-1,3a=2,2a-1,3a=0,9a
1/3b+1/5b-2/15b=5/15b+3/15b-2/15b=6/15b