smc

Let us represent the number of boys $b$, and the number of girls $g$. From the first sentence, we get that $2(g-15)=b$. From the second sentence, we get $5(b-45)=g-15$. Expanding both equations and simplifying, we get $2g-30=b$ and $5b=g+210$. Substituting $b$ for $2g-30$, we get $5(2g-30)=g+210$. Solving for $g$, we get $g=\boxed{40}$.