a)
\(\frac{x}{2}=\frac{y}{3};\frac{y}{4}=\frac{z}{5}\Leftrightarrow\frac{x}{8}=\frac{y}{12}=\frac{z}{15}=\frac{x+y-z}{8+12-15}=\frac{10}{5}=2\)
x =8.2 =16
y =12.2 =24
z=15.2 =30
b) \(\frac{x}{3}=\frac{y}{-2}=\frac{z}{4}=\frac{4x+y-2z}{4.3+\left(-2\right)-2.4}=-\frac{18}{2}=-9\)
x =-9.3 =-27
y =-9.(-2) = 18
z =-9.4 = -36