Question

There Are 12 More Students Taking History Than Math. There Are Twice As Many Students Taking Psychology As There Are Students Taking Math. There Are 452 Students Enrolled In These Three Subject. Assume Each Student Is Taking Only One Of These Three Courses. How Many Are Taking History? How May Are Taking Math?

Answer 1

what have they told you?
h = m+12
p = 2m
h+m+p = 452
Now solve. Substitution is probably easiest.

Answer 2

86