to add or subtract fractions you need to find a common denominator
8 doesn't go directly into 20 but both 8 and twenty can go into 40
so to get 8 into 40 we have to multiply both top and bottom of the fraction by 5 making 5/40
to make 20 go into 40 we have to multiply both top and bottom by 2 making
26/40
5/40+26/40
only add the top numbers
31/40
31 is a prime number so can not reduce any more
final answer is 31/40