math
posted by lisa .
if the ratio of boys to girls is 3/4 and there are 49 students how many boys are there?

3/7 = x/49
Cross multiply and solve for x. 
75

Does 75 make sense? There are only a total of 49 students.
This site explains how to solve a problem with a proportion.
http://www.aaamath.com/ratpropcrossx.htm 
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