To find the ratio of girls to boys in the 7th-grade class, you can divide the number of girls by the number of boys.
The number of girls is 300, and the number of boys is 250.
So, the ratio of girls to boys is:
\[ \text{Ratio} = \frac{\text{Number of girls}}{\text{Number of boys}} = \frac{300}{250} \]
To simplify this ratio, divide both numbers by their greatest common divisor, which is 50 in this case:
\[ \frac{300 \div 50}{250 \div 50} = \frac{6}{5} \]
Thus, the ratio of girls to boys in the class is 6:5.