How many bottles each holding 1/4 litre can be filled from 7 1/2 litres
$$7 \frac{1}{2} \text{ litres} \\\\
=\frac{15}{2}\text{ litres} \\\\
=\frac{15}{2}*\frac{2}{2} \text{ litres} \\\\
=\frac{30}{4} \text{ litres} \\\\
=30\times \frac{1}{4} \text{ litres}$$
30 bottles