b) x+y=24
[tex] \frac{x}{5}= \frac{y}{7} [/tex] ⇒ 7x=5y
[tex] \frac{5y}{7}+y=24 [/tex]
aducem la numitor comun adica 7 si vom avea
5y+7y=168
12y=168
y=168:12
y=14
[tex]x= \frac{5*14}{7}=5*2=10 [/tex]
c) x+y+z=15
[tex] \frac{x}{4} = \frac{y}{5} = \frac{z}{6} [/tex]
[tex]5x=4y =\ \textgreater \ x= \frac{4y}{5} [/tex]
[tex]6y=5z =\ \textgreater \ z= \frac{6y}{5} [/tex]
[tex] \frac{4y}{5}+y+ \frac{6y}{5}=15 [/tex]
aducem la numitor comun adica 5 si vom avea
[tex]4y+y+6y=75[/tex]
[tex]15y=75[/tex]
[tex]y=75:15[/tex]
[tex]y=5[/tex]
[tex]x= \frac{4*5}{5} =4[/tex]
[tex]z= \frac{6*5}{5} =6[/tex]
