.5 is basically 1/2. We know this because .5 written as a fraction is 50/100 which you can simplify to 1/2.
6/10 is greater than 1/2. You can find this out by converting 1/2 to tenths. Multiply the numerator and the denominator by 5 to get 5/10. From there you can easily see that 6/10 > 5/10.
As for the number line simply use 10ths: 1/10, 2/10, 3/10 ... and input 6/10 and 5/10 in the appropriate areas.