Greetings!
The best way to compare fractions is to find the LCM (The Lowest Common Denominator) of each of the fractions. This can be done simply by listing the multiples of the denominators.
Multiples:
3: 3,6,9,12,15,18,21,24,27...210,213
10:10,20,30,40,60,70,80...210,220
6: 6,12,18,24,30,36,42,48...210,216
7: 7,14,21,28,35,42,49...210,217
The LCM is 210:
3*70=210
10*21=210
6*35=210
7*30=210
Now, we must do what we do the denominators to the numerators:
1*70=70
70/210
2*21=42
42/210
1*35=35
=35/210
2*30=60
=60/210
The fraction with the largest numerator has the greatest value; In this case it 1/3 or 70/210.
Hope this helps.
-Benjamin