The ratio of number a to number b is equal to:
[tex]\frac{a}{b}[/tex]So, the ratio of the number of boys to the number of girls is:
[tex]\frac{15}{12}[/tex]Now, we can divide both numbers by a common factor and get an equivalent ratio as:
[tex]\frac{15}{12}=\frac{\text{ 15/3}}{12\text{ / 3}}=\frac{5}{4}[/tex]Therefore, the ratio is 5/4
Answer: 5/4