Answer:
5 boys
Explanation:
Write it like this:
3/X=12/20
Then, cross multiply.
3*20=60
X*12=12X
12X=60
Divide both sides by 12
60/12=5
X=5
The unknown number is 5
If there are 3 girls, then there are 5 boys.
5
ratio = 12:20
12/4 = 3
so we do
20/4 = 5
there are 5 boys
Another way, we can write it as a fraction
12/20 = 3/x
12x = 60
x = 5
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