Equal sharing means division: divide the total number of cakes by the number of pupils.<br><br>
&bull; 5 cakes ÷ 7 pupils = \( \frac{5}{7} \) of a cake per pupil<br>
&bull; \( \frac{5}{7} \) is already in simplest form (HCF of 5 and 7 is 1).<br><br>
Final Answer: B: \( \frac{5}{7} \)