Simple math.
First of all to know the greatest fraction you have to make this fraction's denominator all the same.
so you need to get the LCD of the denominators
LCD or Lowest Common Denominator
We need to list the possible number first.
For 8 we have,
0, 8, 16, 24, 32, 40, 48, 56, 64
For 6,
0, 6, 12, 18, 24, 30, 36, 42, 48
For 3,
0, 3, 6, 9, 12, 15, 18, 21, 24, 27
Now get the LCD.
The LCD of all will be 24.
Meaning 24 will be the new denominator of all.
Now it's time to know the new numerator.
To get it, divide the LCD to the denominator and multiply the result to the numerator.
example.
for 1/8,
24 / 8 = 3 * 1 = 3 (new numerator)
therefore
1/8 will be 3/24
next
for 1/6
24 / 6 = 4 * 1 = 4
therefore
1/6 will be 4/24
and lastly,
for 1/3
24 / 3 = 8 * 1 = 8
therefore
1/3 will be 8/24
And now for your real question
What is the greatest fraction?
Compare the three new fractions
We have,
3/24, 4/24, 8/24
It won't be that difficult now, since we have to know what has the highest numerator.
In this case 8/24 is the highest.
therefore,
1/3 is the greatest fraction
I hope that helps.