Răspuns:
c. 15 cm
Explicație pas cu pas:
AB || CD => ΔAOB ~ ΔCOD
[tex]\frac{AB}{CD} = \frac{OB}{OD} \iff \frac{AB}{AB + CD} = \frac{OB}{OB + OD} \\ \frac{AB}{AB + CD} = \frac{OB}{BD} \iff \frac{24}{24 + 8} = \frac{OB}{20} \\\frac{24}{32} = \frac{OB}{20} \iff OB = \frac{24 \cdot 20}{32} \\ \implies \bf OB = 15 \ cm[/tex]