Goals/Misses=3/7 right?
 
so we can set up a proportion;
if she scores 24 goals it would go on top of the fraction to the left leaving an x in the bottom for misses
 
24/x=3/7      then you cross multiply getting
24(7)=3(x)   so simplify
168=3x          now divide both sides by 3
56=x
 
She missed 56 goals at practice.