On a class of 250 students,175 take mathematics and 142 take science. If every student takes at least one subject, how many takes both mathematics and science.
We can find the number of students who take both mathematics and science by finding the intersection of the two groups.
Using the principle of inclusion-exclusion, we can add the number of students who take mathematics to the number of students who take science and then subtract the total number of students to get the number of students who take both subjects.
So, the number of students who take both mathematics and science is:
175 + 142 - 250 = 317 - 250 = <<175+142-250=67>>67
Therefore, 67 students take both mathematics and science.