20. prima simplificăm fracție prin 14.
[tex] \frac{3}{n} = \frac{14}{42} [/tex]
[tex] \frac{3}{n} = \frac{1}{3} [/tex]
[tex] \frac{1}{n} [/tex]
21.
[tex] \frac{a + 2}{39} = \frac{7}{13} [/tex]
[tex]13(a + 2) = 273[/tex]
[tex]a + 2 = 21[/tex]
[tex]a = 21 - 2[/tex]
[tex]a = 19[/tex]
17.
12+8=20
P=12/20/0,6
19.
3 supra 6 = 4 supra 8
9.
c=13%
ms=100g
md=?
c/100=md/ms
md=c•ms/100=13•100/100=23g
8.
md=40g
m=200+40=240
c=md/m×100=40/240×100=100/6=16.66%
6.
a=13b/20
b.....100%
13b/20....x
x=13b/20×100/b=65%
2.
a/b=5
a/12,4=5/1
a=5•12,4
a=62
1.
x/y=3/7
y/z=7/12
x/z=?
x=3y/7
z=12y/7
x/z=3y/7/12/7=3y/7•7/12y=
1/4
