Obliczamy, ile kosztuje litr soku w kolejnych kartonach:

$\underline{\underline{\text{karton I}}}$

$7:0,25=\frac{7}{0,25}=\frac{700}{25}=28\text{zł}$

$\underline{\underline{\text{karton II}}}$

$8,30:0,3=83:3=\frac{83}{3}=27\frac{2}{3}=27,666\dots \approx 27,67\text{zł}$

$\underline{\underline{\text{karton III}}}$

$49,50:1,8=495:18=\frac{495}{18}=\frac{165}{6}=\frac{55}{2}=27,50\text{zł}$

$\underline{\underline{\text{karton IV}}}$

$126:4,5=1260:45=\frac{1260}{45}=\frac{420}{15}=\frac{140}{5}=28\text{zł}$

$odp.C$