What are the answer and how do i solve it

I'll answer 3 of these questions. 
For future notice, make sure to limit yourself to asking at most, 3 individual questions per question. :)

1) r/10+4=5
Subtract both sides by 4.
(r/10+4)-4=(5)-4
r/10=1
Multiply both sides by 10.
(r/10)*10=(1)*10
r=10

2) n/2+5=3
Subtract 5 from both sides.
(n/2+5)-5=(3)-5
n/2=-2
Multiply both sides by 2.
(n/2)*2=(-2)*2
n=-4

3) 3p-2=-29
Add 2 to both sides.
(3p-2)+2=(-29)+2
3p=-27
Divide both sides by 3.
(3p)/3=(-27)/3
p=-9

Hope this helps.
-Benjamin

Best answer that i found on yahoo ok   set :   x= length of 2nd piece in cm  x- 3= length of 1st piece in cm  x-4= length of 3rd piece in cm  then since you know they all came from the 20 cm ribbon you add them together and set them equal to 20x+ x-3 +x-4 = 20  3x - 7= 20  3x= 27  x= 9  the shortest piece is the third piece which is x- 4  x-4  9-4 = 5  the length of the smallest piece is 5 cm.  the other lengths are  9 cm  6 cm