To compare 7/10 and 1/2 we have to find a common denomator, this can be found by choosing a number thats both in the timestable of 2 and of 10(the denomators). For thisexample you can use 10, one of our fractions is already out to 10 so we only have to do one.
To change 1/2 into a fraction out of 10 we have to do the sme to the bottom as we do to the top. So since we are multiplying the bottom by 5 we have to mutiply he bottom by five. This gives us 5/10.
We can now compare 7/10 and 5/10
From the numerators we can clearly see that 7/10 is a greater value that 5/10 (which was originally 1/2).