(1 3/5+1,8)*1/2 (5,4-2 1/3+0,25)*0,12 (7,6-4 3/4): 1.9

1)  1 3/5=1,6; 1,6+1,8=3,4.
 1/2=0,5; 3,4·0,5=1,7.

2) 5,4=5 2/5=27/5;  2 1/3=7/3; 0,25=25/100=1/4;
27/5 - 7/3 + 1/4=(324-140+15)/60=3 19/60.
0,12=12/100=6/50.
319/60 · 6/50=959/300=3 59/300.

3) 7,6-4 3/4=7,6-4,75=3,85;
3,85 : 1,9=3 17/20 / 19/10=77/20 ·10/19=2 1/38.