1/3（6+x）=2.8
2+(1/3)x=2.8
(1/3)x=0.8
x=2.4
27-1.7x=13.4
1.7x=27-13.4
1.7x=13.6
x=8
4/5x+120=x
120=x-4/5x
120=1/5x
x=600