a) $\frac{a}{2}=\frac{b}{1}=\frac{c}{3}=\frac{a+b+c}{2+1+3}=\frac{48}{6}=8$
Suy ra a = 16; b = 8; c = 24.
b) $\frac{a}{2}=\frac{b}{3};\frac{b}{2}=\frac{c}{3}$ do đó $\frac{b}{3}=\frac{2c}{9}=\frac{c}{4.5}$
Suy ra $\frac{a}{2}=\frac{b}{3}=\frac{c}{4.5}=\frac{a+c}{6.5}=\frac{26}{6.5}=4$
Vậy a = 8; b = 12; c = 18