The sum of a triangle's angles are 180 so since you know one angle is 80, you would put 2x + 80 = 180, which would be 2x = 100, which simplifies to x = 50
lets say there are 100 girls. 4/5 of 100 is 80, so 80 girls have brown hair. 3/4 of the 80 who have brown hair have long hair. 3/4 of 80 is 60. so we know that out of 100, 60 have long brown hair. in simplest fraction form, 60/100= 3/5
