Verified answer

х*16/8=80

х*2=80

х=80:2

х=40

34*х-12=260

34х=272

х=272:34

х=8

180/х*4=24

180:х=24:4

180:х=6

х=180:6

х=30

2400/(317+х)=3

317+х=2400:3

317+х=800

х=800-317

х=483