57,4:4+1 1/6 :4 2/3 -(2,7+5 1/20)*0,8 =7 1033/1120
1)2,7+5,05=7,75
2)57,4:4=14,35
3)1 1/16:4 2/3=17/16*3/14=51/224
4)7,75*0,8=6,2
5)14,35+51/224-6,2=8,15-51/224=8 3/20-51/224=8 168/1120-255/1120=
=7 1288/1120-255/1120=7 1033/1120
2 1/15 -(1 2/3 +1/5)=2 1/15-1 10/15-3/15=1 16/15-1 10/15-3/15=6/15-3/15=3/15=1/5