Jawabanmu

2014-02-03T19:31:51+07:00
3z+11=-28
28+11=-3z
39=-3z
z=-13

25-4y=6y+15
25-15=6y+4y
10=10y
1=y
2014-02-03T19:33:00+07:00
1.3z + 11 = -28
           3z = -28 - 11
           3z = -39
             z = -39/3
             z = -13

2. 25-4y = 6y + 15
    -4y -6y= 15 - 25
    10y = -10
        y = -10/10 = -1

mudah-mudahan bener :)