b) [tex]\frac{3}{10} = \frac{x}{4}[/tex]
[tex]\frac{3}{10} = \frac{1,2}{4}[/tex]
[tex]0,3 = 0,3[/tex]
c) [tex]\frac{3}{x} = \frac{7}{x+5}[/tex]
[tex]\frac{3}{3,75} = \frac{7}{3,75+5}[/tex]
[tex]0,8 = \frac{7}{8,75}[/tex]
[tex]0,8=0,8[/tex]
d) [tex]\frac{a+3}{5} = \frac{7}{5}[/tex]
[tex]\frac{4+3}{5} = \frac{7}{5}[/tex]
[tex]\frac{7}{5} = \frac{7}{5}[/tex]
