Răspuns:
4. a)
[tex] \frac{5}{9} = \frac{10}{x} [/tex]
5•x=9•10
5x=90
x=90:5
x=18
b)
[tex] \frac{10}{12} = \frac{15}{x} [/tex]
10•x=12•15
10x=180
x=180:10
x=18
c)
[tex] \frac{6}{x} = \frac{2}{5} [/tex]
2•x=6•5
2x=30
x=30:2
x=15
5.
a)
[tex] \frac{3x + 2}{5x + 4} = \frac{7}{12} [/tex]
(3x+2)•12=(5x+4)7
36x+24=35x+28
36x-35x=28-24
x=4
b)
[tex] \frac{x + 2}{x - 1} = \frac{7}{6} [/tex]
(x+2)•6=(x-1)•7
6x+12=7x-7
7x-6x=7-6
x=1
