120 .
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Explanation:
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15% of x = 18 ; x = total number of students.
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Solve for: "x" ; which is our answer.
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15 % of x = (15/100) * x = (0.15)x ;
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(0.15) x = 18 ;
Divide each side by: "(0.15)" ; to isolate "x" on one side of the equation; and to solve for "x" , which is our answer:
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(0.15)x / (0.15) = 18 /(0.15) ;
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x = 120 ; They are 120 students in Mrs. Madison's math classes.
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The question asks to type the answer as a number. So:
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120 .
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