It appears Jake said 5-2 = 3 for the denominator portions. This is not correct. In order to subtract fractions, the denominators must be the same and they stay the same the entire time. Only the numerators (aka stuff up top) are being subtracted.
Currently 3/5 - 1/2 cannot be subtracted since the 5 and 2 are different denominators. But we can say this:
3/5 = 6/10
1/2 = 5/10
and then from there, we can say:
3/5 - 1/2 = 6/10 - 5/10 = (6-5)/10 = 1/10
So in short,
3/5 - 1/2 = 1/10