Answer is the ratio 1 : 4
Work Shown
x = number of black pants
y = number of blue pants
z = number of brown pants
x = (5/6)y
x = (5/9)z
z = (9/5)x
x+y+z = total number of pants
x+y+z = (5/6)y + y + (9/5)x
x+y+z = (5/6)y+y+(9/5)*(5/6)y
x+y+z = (5/6)y+y+(3/2)y
x+y+z = (5/6)y+(6/6)y+(9/6)y
x+y+z = ( (5+6+9)/6 )y
x+y+z = (20/6)y
x+y+z = (10/3)y
numberOfBlackPants : Total
(5/6)y : (10/3)y
6*(5/6)y : 6*(10/3)y
5y : 20y
5 : 20
1 : 4
The ratio of the number of black pants to the total number is 1 : 4
It means the total is 4 times that of the number of black pants.