Question

ajutatima la b si c dau 15 pct

Answer 1

b)      x+y=24
$\frac{x}{5}= \frac{y}{7}$   ⇒   7x=5y
$\frac{5y}{7}+y=24$
aducem la numitor comun adica 7 si vom avea 

5y+7y=168
12y=168
y=168:12
y=14
$x= \frac{5*14}{7}=5*2=10$

c)  x+y+z=15
$\frac{x}{4} = \frac{y}{5} = \frac{z}{6}$
 $5x=4y =\ \textgreater \ x= \frac{4y}{5}$
$6y=5z =\ \textgreater \ z= \frac{6y}{5}$

$\frac{4y}{5}+y+ \frac{6y}{5}=15$
aducem la numitor comun adica 5 si vom avea 
$4y+y+6y=75$
$15y=75$
$y=75:15$
$y=5$
$x= \frac{4*5}{5} =4$
$z= \frac{6*5}{5} =6$