Explicație:
6.
[tex] \frac{a}{9} = \frac{b}{11} = \frac{c}{14} = \frac{a + b + c}{9 + 11 + 14} = \frac{680}{34} = 20[/tex]
[tex] \frac{a}{9} = 20 \\ a = 20 \times 9 \\ a = 180[/tex]
[tex] \frac{b}{11} = 20 \\ b = 20 \times 11 \\ b = 220[/tex]
[tex] \frac{c}{14} = 20 \\ c = 20 \times 14 \\ c = 280[/tex]
Verificare:
180+220+280=680✔️
7.
[tex] \frac{a}{3} = \frac{b}{11} = \frac{c}{5} [/tex]
Dupa amplificam prima fractie cu 3,si pe ultima cu 2 si vine asa
[tex] \frac{3a}{9} = \frac{b}{11} = \frac{2c}{10} = \frac{3a + b +2c }{9 + 11 + 10} = \frac{300}{30} = 10[/tex]
[tex] \frac{3a}{9} = 10 \\ 3a = 10 \times 9 \\ 3a = 90 \\ a = 30[/tex]
[tex] \frac{b}{11} = 10 \\ b = 10 \times 11 \\ b = 110[/tex]
[tex] \frac{2c}{10} = 10 \\ 2c = 10 \times 10 \\ 2c = 100 \\ c = 100 \div 2 \\ c = 50[/tex]
Verificare:
3*30+110+2*50=90+110+100=300✔️
