text: if 45% of the school are boys and there are 858 girls, how many boys are enrolled? i need to know how to set problem up. ninoguapo also didn't use a spell-checker!  the answer is 702. here's how to get the answer.  the other way to say what this question is asking is this: if the school is 45% boys and 55% girls (which we know), then that means that the 858 girls are 55% of the total number in the school.  "but," you say, "55% of what????"  you can compare it using a ratio: 858 over "some magical unknown number" is the same as 55 over 100. so multiply 858 by 100, and then divide the answer by 55. that means the "magical unknown number" turns out to be 1,560...that's how many students there are in the school.  take out the girls (858) from the total (1,560) and you get...702. that's 45% of 1,560.