((23,79:7,8-6,8:17)х3,04-2,04)х0,85=5,1136

1.  23,79:7,8=3,05

2.  6,8:17=0,4

3.  3,05-0,4=2,65

4.  2,65*3,04=8,056

5.  8,056-2,04=6,016

6. 6,016*0,85=5,1136