Question 174573
let x="students enrolled in all three"


"170 are enrolled in both Math and English" __ so 170-x are enrolled in ONLY Math and English


"150 are enrolled in both History and English" __ so 150-x are enrolled in ONLY History and English


"300 are enrolled in Math and History" __ so 300-x are enrolled in ONLY Math and History


"500 students are enrolled in at least two of these three classes"
so (170-x)+(150-x)+(300-x)+x = 500


620-2x=500


120=2x


60=x