Pretvorimo sva vremena u decimalni zapis radi usporedbe:
- Ana: $12.4 = 12.400\text{ min}$$12.4 = 12.400\text{ min}$
- Lea: $12\frac{3}{8} = 12 + 0.375 = 12.375\text{ min}$$12\frac{3}{8} = 12 + 0.375 = 12.375\text{ min}$
- Marko: $12.38 = 12.380\text{ min}$$12.38 = 12.380\text{ min}$
- Petra: $12\frac{1}{3} = 12 + 0.333\ldots = 12.333\ldots\text{ min}$$12\frac{1}{3} = 12 + 0.333\ldots = 12.333\ldots\text{ min}$

Najbrži trkač je onaj s **najmanjim** vremenom.
$$12.333\ldots < 12.375 < 12.380 < 12.400$$$12.333\ldots < 12.375 < 12.380 < 12.400$
Najmanje vrijeme ima Petra.

Točan odgovor: **D) Petra**