9514 1404 393
Answer:
Step-by-step explanation:
The difference is 7-5 = 2 "ratio units", corresponding to a difference of 36 dancers. Then each "ratio unit" stands for 36/2 = 18 dancers.
There are 7×18 = 126 girls.
There are 5×18 = 90 boys.
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You could solve this by writing some equations:
g/b = 7/5
g -b = 36
Then you could substitute for g:
(36+b)/b = 7/5
36/b +1 = 2/5 +1 . . . . expand the fractions
36/b = 2/5 . . . . . . . . . subtract 1
b = (5/2)(36) = 90 . . . multiply by 5/2b
g = 36+90 = 126
