Answer:
The total number of girls and boys are at the concert will be 756.
Since the ratio of girls to guys at the concert is 4 to 5 and there are 336 girls at a concert, then the total girls and boys are at the concert will be:
= 336 / (4/9)
= 336 × 9/4
= 756
Therefore, the total girls and boys are at the concert will be 756.