Adults = 415.<br>
There are 90 more adults than children.<br><br>
&bull; Adults = Children + 90<br>
&bull; So Children = Adults &minus; 90<br>
&bull; = 415 &minus; 90 = 325<br>
<br>
There are 325 children at the concert.<br>
Check: 325 + 90 = 415. ✓