Lời giải:

a. $y+30\text{%}y=-1,3$

$y+0,3y=-1,3$

$y(1+0,3)=-1,3$

$y.1,3=-1,3$

$y=(-1,3):1,3=-1$

b.

$y-25\text{%}y=\frac{1}{2}$

$y-0,25y=0,5$

$y(1-0,25)=0,5$

$y.0,75=0,5$

$y=0,5:0,75=\frac{2}{3}$

c.

\(3+\frac{1}{3}y+16+\frac{3}{4}=-13,25\)

$\frac{1}{3}y+19,75=-13,25$
$\frac{1}{3}y=-13,25-19,75=-33$
$y=-33:\frac{1}{3}=-99$

y+30%y=-1,3

y+3/10y=-1,3

y(1+3/10)=-1.3

y.13/10=-13/10

y=-13/10:13/10=-1

b,y-25%y=1/2

y-1/4y=1/2

y(1-1/4)=1/2

y.3/4=1/2

y=1/2:3/4=2/3

c,3/1/3y+16/3/4=-13,25

10/3y+67/4=53/4

10/3y=53/4-67/4=-7/2

y=-7/2:10/3=-21/20

7/10=1/2=1/5;10/21=1/3+1/7;7/8=1/8+1/4+1/2

a, y + 30%y = -1,3

 1.y + 30/100y = -13/10

 1.y + 3/10y  = -13/10

(1 + 3/10). y = -13/10

13/10 .y = -13/10

           y = -13/10 : 13/10

           y = -13/10 . 10/13

           y = -1

b, y - 25%y = 1/2

   1.y - 25/100.y = 1/2

   1.y - 1/4.y = 1/2

   (1 - 1/4) y = 1/2

    3/4 .y = 1/2

           y = 1/2 : 3/4

           y = 1/2 . 4/3

           y = 2/3

câu c mik chưa nghĩ ra

e chia từng bài ra nhe

giúp mik với mai mik nộp cho rồi :((