1) 3.5х-2.3x+3.8=4.28
1.2x=4.28-3.8=0.48
x=0.48/1.2=0.4
2) 4.7y-(2.5y+12.4)=1.9
4.7y-2.5y-12.4-1.9=0
2.2y-14.3=0
2.2y=14.3
y=14.3/2.2=6.5
3) (8.3-k)4.7=5.64
39.01-4.7k=5.64
-4.7k=5.64-39.01=-33.37
k=33.37/4.7=7.1
4) (9.2-m)3.2=16
29.44-3.2m=16
-3.2m=16-29.44=-13.44
m=13.44/3.2=4.2