Answer :

naǫ
[tex]\frac{14}{40} \times 100\%=\frac{7 \times 2}{20 \times 2} \times 100\%=\frac{7}{20} \times 100\%=7 \times \frac{100}{20} \%=7 \times 5\%=35\%[/tex]

35% of the marbles are red.