To find the ratio of boys to girls in the chorus, we can express it as:
\[ \text{Ratio of boys to girls} = \frac{\text{Number of boys}}{\text{Number of girls}} = \frac{12}{20} \]
Next, we simplify this fraction. Both the numerator and the denominator can be divided by 4:
\[ \frac{12 \div 4}{20 \div 4} = \frac{3}{5} \]
Thus, the ratio of boys to girls is \(3:5\).
The correct response is:
3:5
3 colon 5