 
<translate> Bari maza su zama X, sannan mata su zama 7X, duka = X+7X = 8X Don haka ya kamata ya zama ninki 8, 30 ba ninki 8 ba ne. Amsar ƙarshe: (C). <eng> Let the boys are X, then girls are 7X, total = X+7X = 8X
So it should be multiple of 8, 30 is not a multiple of 8.
The final answer: (C). 