Let x represent the number of boys at the high school.
1/8x total tried out for football.
1/6 total tried out for baseball.
If we were to draw a Venn diagram, the intersection of the two circles would be the 1/12 of the students that tried out for both, or 1/12x.
Taking this away from the total of 1/8x for football,
1/8x - 1/12x
3/24x - 2/24x
1/24x tried out for just football.
Taking the 1/12x away from the 1/6x that tried out for just baseball,
1/6x - 1/12x
4/24x - 2/24x
2/24x = 1/12x tried out for just baseball.
Looking at those that tried out for football, 2/24 tried out for both and 3/24 total tried out for football. This means 2 out of 3, or 2/3, of the football try outs also tried out for baseball.